JP2000215494A - Optical pickup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup having high economic efficiency of light, detecting (reproducing) recording information on a medium with high speed/high spatial resolution and being realizable with simple constitution. SOLUTION: This pickup is constituted so that a flexible optical waveguide 41 of a nearly rhabdo-shape is used, and a reflection surface 44 reflecting at least a partial beam propagating through a core 42 in the direction transmitting through a clad 43 is provided on one end side of the optical waveguide 41, and a light shield film 45 shielding transmission of light is formed on the clad surface making the place that the light reflected by the reflection surface 44 transmits through a center, and further, by canceling a part of the light shield film 45 corresponding to the place where the light reflected by the reflection surface 44 transmit through and forming an opening 46 smaller than the wavelength of the light, the optical pickup of a cantilever shape generating the near field light from the lower surface of the tip is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup (head) for recording and reproducing information in an optical information storage device using near-field light.

[0002]

2. Description of the Related Art In recent years, images (still images, moving images), sound, etc.
There is an increasing demand to simultaneously process (multiplex information processing) a plurality of types of information having a large data amount, and this has further accelerated the demand for faster, higher-density, large-capacity, and low-cost information storage devices. I have. Typical external storage devices for computers include, for example, magnetic disk devices and optical (magneto-optical) disk devices.

[0003] Of these, the magnetic disk drive is provided at the end of the slider core by photolithography technology.
Information is recorded by generating a minute magnetized region on a recording medium made of a hard magnetic material by a leakage magnetic field from a minute ferromagnetic core. In addition, information is reproduced by detecting a weak leakage magnetic field from the magnetization of the medium using a magnetoresistive element formed of an extremely thin ferromagnetic material.

A magnetic disk drive is capable of high-speed access and high-speed data transfer due to its simplicity in the mechanical configuration and the reduction in size and weight of a movable part including a head part. It has become the representative external storage device in the system.

However, in the magnetic disk device, the recording magnetization region (volume) is drastically reduced as the recording density is increased, and it is difficult to stably maintain the recording magnetization (recorded information) due to thermal disturbance. It is said that there is a density limit.

On the other hand, an optical disk device records information by changing optical characteristics such as a reflectance and a polarization rotation angle of a recording medium with a focused high-intensity laser beam, irradiates a weak beam, and reflects the reflected light. Alternatively, it is an apparatus for reproducing information by detecting a slight change in the optical characteristics from transmitted light.

Generally, in an optical disk device, as described above, recording is performed by utilizing the change in the optical characteristics of a recording medium. Therefore, the limit of the recording density at which information retention becomes unstable due to thermal disturbance is limited to that of a magnetic disk device. This is a higher recording density area than that.

[0008] As described above, the optical disk device is superior to the magnetic disk device in terms of the limit of increasing the density of information, but basically, a fine bit is recorded by focusing a laser beam with a lens. The size of the minimum recording bit is limited by the diffraction limit of light.

As a means for overcoming this limitation,
There has been proposed a form in which a lens having an extremely small focal length of a submicron and a large numerical aperture is positioned 100 nm to several 100 nm above the medium by applying a floating head slider technology of a magnetic disk device to perform proximity recording.

FIG. 1 shows an example of an optical pickup for recording / reproducing in a conventional optical information storage device. Here, an objective (main condensing) lens 22 and a main lens 22 mounted on a back surface of a slider 21 made of a transparent material are shown. A laser beam narrowed down to a submicron diameter by a pseudo hemispherical solid immersion lens (SIL) 23 fixed to the slider 21 itself,
The recording / reproducing is performed by irradiating the recording layer 11 of the optical recording medium 10 via a floating clearance (working distance of the SIL 23) of about 100 nm.

At this time, the slider 21 has a laser light source 24
Is supported in a floating state on the fixed side of the pickup on which the slider is disposed via a slider supporting suspension 25.
The laser beam from the light source 24 is separated from the suspension 25 by a mirror (or prism) 2 fixed to the tip of a mirror supporting arm 26 extending to the rear side of the slider 21.
The direction is changed by 7 so as to be incident on the objective lens 22 and the SIL 23 mounted on the slider 21.

FIG. 2 shows another example of an optical pickup for recording / reproducing in a conventional optical information storage device. Here, laser light from a light source (not shown) is applied to an optical fiber 28.
Is guided to the vicinity of the slider 21 using the slider 21.
An example is shown in which the direction is changed by a mirror 29 fixedly disposed on the slider 21 so as to be incident on a condenser lens 30 also mounted on the slider 21.

These are based on the optical recording system, but skillfully utilize the mechanism of the magnetic disk drive in the mechanism section. No focusing control is required, and the recording bit is set by bringing the objective or condenser lens close to the medium surface. Can be miniaturized, and high-density recording is enabled. Also, since the mass of the movable part can be significantly reduced as compared with the conventional optical head, it can be accessed at a high speed, though not comparable to the magnetic disk drive, and the volume density of the device can be improved by stacking media (loading). This is effective for improving the storage capacity.

In these close focus light recording systems, as described above, although the size of the focused beam spot has been reduced as compared with the conventional optical disk apparatus (remote light focus system), the short wavelength of the light source expected in the future is expected. Even if the height of the slider mounted with the lens is reduced, there is a limit to miniaturization of the condensed spot which is theoretically possible. In addition, the precision of alignment of individual optical components is increasingly strict, and it is difficult to reduce costs and secure reliability.

As a method for further overcoming these problems, in particular, the limit of miniaturization of the condensed spot, an aperture finer than the wavelength of light is used.
2. Description of the Related Art An optical information storage device using near-field light that is standing without propagating in the range of nm has been proposed.

FIG. 3 shows still another example of an optical pickup for recording / reproducing in a conventional optical information storage device, here an example using near-field light. That is, the tip 32 of the optical fiber 31 for guiding the laser light from a light source (not shown) is sharpened, and the metal light-shielding film (not shown) formed in the vicinity of the tip 32 is removed in the minute area to thereby remove the tip. 32, a very small opening of 100 nm or less is formed,
The optical fiber 31 is mounted on the slider 21, and the medium 1 is exposed to the tip of light (near-field light) 33 that seeps out of the minute opening.
By scanning 0, bit reproduction from submicron to sub-submicron is enabled.

[0017]

However, in the above-mentioned optical pickup, of the light incident on the optical fiber 31,
Since the ratio of the amount of light that exudes from the tip 32 and can be used as the tip of the microscopic light 33 is extremely small, and the amount of light that can be received by the photodetector 34 is insufficient, information transmission / reception speed equivalent to that of a normal file storage device is realized. That was very difficult. Further, it is necessary to define the tip 32 of the optical fiber 31 on the order of 10 nm in accordance with the flying surface (air bearing surface (ABS) surface) of the slider. It has been difficult to apply it as a head (pickup) for a file storage device.

[0018]

According to the present invention, in order to solve the above-mentioned problems, a flexible, substantially rod-shaped optical waveguide having a core and a clad is used. By providing a reflecting surface that reflects at least part of the light in a direction that transmits the clad, an optical path of propagating light in the core is bent, and a light-shielding film is provided at a portion where the propagating light transmits through the clad and is further used. It is characterized by providing a minute aperture smaller than the wavelength of light, and its purpose is to realize an optical pickup capable of detecting (reproducing) recorded information of a medium with high spatial resolution with an extremely simple configuration.

In the above-mentioned optical pickup, the cross-sectional area of the core is formed so as to gradually decrease from the other end to the one end of the optical waveguide. An object of the present invention is to realize an optical pickup capable of efficiently narrowing an incident beam and obtaining a reproduced signal having a high light use efficiency and a high S / N ratio.

In the above optical pickup, a spherical or hemispherical, spheroidal, or paraboloid of revolution having a different refractive index from the cladding is provided in a portion of the cladding where the light reflected by the reflecting surface is transmitted. An object of the present invention is to provide an optical pickup capable of efficiently narrowing an incident beam just above a minute opening and obtaining a reproduced signal having a high light use efficiency and a high S / N ratio. Is to make it happen.

Further, in the above optical pickup, an optical waveguide having at least two cores is used, and reflected light of light propagating in each of the at least two cores is on one straight line substantially coincident with the longitudinal direction of the optical waveguide. The purpose of the invention is to realize an optical pickup capable of recording information with a simple configuration.

In the above optical pickup, an optical waveguide having at least two cores is used, and reflected light of light propagating in each of the at least two cores is on one straight line substantially coincident with the longitudinal direction of the optical waveguide. It is characterized in that a concave portion is provided on the clad surface of a portion where the reflected light is transmitted, and a lens having a convex cross section is formed in the concave portion, the purpose of which is to record finer bits. An object is to realize an optical pickup with a simple configuration.

In the above-mentioned optical pickup, a stepped portion having a stepped shape or an inverted stepped shape toward one end of the optical waveguide is provided near a portion where the light shielding film is formed or near the opening. It is an object of the present invention to realize an optical pickup having a simple configuration in which the set tolerance of the pickup is relaxed when the apparatus is configured and the floating pickup is excellent in floating stability.

In the above optical pickup, a rigid beam-shaped portion for supporting the optical waveguide and a rigid base constituting the fixed side of the pickup are integrally formed with a soft leaf-shaped portion having a spring property therebetween. And a joint formed with the beam-shaped part of the suspension is provided in the optical waveguide, and the light-shielding film on one end side of the main body is elastically supported by the suspension. It is an object of the present invention to realize an optical pickup having excellent floating stability, high in-plane support rigidity, and capable of high-speed track seek with a simple configuration.

Further, in the above optical pickup, at least a part of the light propagating in the core and traveling straight through the reflection surface is returned to the reflection surface on the extension of the reflection surface on one end side of the optical waveguide. The present invention is characterized in that a reflection surface is formed, and an object thereof is to realize an optical pickup which can access a medium on one side with a simple configuration.

Finally, the optical pickup is characterized in that a notch is formed in a part of the cladding of the optical waveguide, and a solid displacement element is bonded to the notch, the purpose of which is to enable high-speed microtracking. A simple optical pickup is realized with a simple configuration.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings.

FIG. 4 shows a first embodiment of the optical pickup of the present invention. In the figure, reference numeral 41 denotes a substantially rod-shaped optical waveguide having flexibility, 42 denotes a core (part) of the optical waveguide 41, 43 is a cladding (part) surrounding the core 42, 44 is a reflection surface, 45 is a light shielding film (shown by hatching in the figure),
46 is a (micro) opening.

The reflection surface 44 reflects at least a part of the light propagating in the core 42 in a direction transmitting the clad 43.
It consists of one end face of the optical waveguide 41 cut at an angle of 5 degrees. The light-shielding film 45 is for blocking the transmission of light, and has a clad surface centered on a portion through which the light reflected by the reflection surface 44 is transmitted, here, a lower surface on one end side of the optical waveguide 41 and a side surface. And part of the end face (not shown in FIG. 4)
And formed. The opening 46 is for generating near-field light, the size of which is smaller than the wavelength of the light to be used, and the size of the light shielding film 45 corresponding to the portion through which the light reflected by the reflection surface 44 passes. It is formed by removing a part.

The flexible (flexible) optical waveguide 41 can be realized by using a plastic material having a high light transmission property, for example, PMMA for the core portion and cured epoxy resin for the cladding portion. Well known. Here, the reflection surface (end surface) 4
Although the cutting angle of 4 was set to 45 degrees, the cutting angle does not need to be particularly limited as long as the operation principle described below is not hindered, and an arbitrary cutting angle can be selected as long as the configuration of the present application can be realized.

As the light shielding film 45, a material having a high light absorption / attenuation property is required.
A material that is hardly deteriorated by sliding or the surrounding atmosphere is required, and any material that satisfies these conditions may be used. For example, a material such as Ti, Ta, or Cr can be used. Although not shown, a protective film is formed on the outermost layer of the light shielding film 45 in consideration of durability at the time of contact and sliding with a medium.
Examples of the protective film include a carbon film that has been used for a pickup slider or a magnetic medium of a magnetic disk device, a DLC (diamond-like carbon) film that is a carbon film containing a crystal component at a certain ratio or more, and a SiO film.
_Second- order thin films are conceivable.

According to the pickup using such a flexible optical waveguide, it is possible to form a cantilever-like or foil-like form, and by pressing its surface against a medium,
An air bearing (foil bearing) can be easily realized, and a minute opening serving as a sensor can be maintained at a submicron floating clearance above the medium. Therefore, there is no need to align and join an optical waveguide or an optical fiber to a separately manufactured hard slider core as in the related art, and an optical pickup can be realized with a very simple configuration.

FIG. 5 is a side view for explaining the operation principle of the optical pickup using the example shown in FIG. 4 in more detail. In the figure, 10 is an optical recording medium, 51 is a (laser) light source, 52 is a condensing lens for condensing laser light from the light source 51 and leading it to the core 42 of the optical waveguide 41, 53 is a photodetector, 54 Collects the scattered light from the medium 10 and
3 is a condenser lens.

Hereinafter, the operation principle of the optical pickup having the structure shown in FIG.

The reproduction laser light (CW laser light) emitted from the light source 51 is guided to the core 42 of the optical waveguide 41 by the condenser lens 52, propagates there, and reaches the reflection surface 44 at one end. Here, the light that has propagated through the core 42 has its optical path bent by 90 degrees, passes through the cladding 43, and reaches the lower surface of the optical waveguide 41 (the surface facing the medium 10). Optical waveguide 4
A light shielding film 45 is formed on the lower surface of
At the irradiation (arrival) point of the laser light beam whose optical path is bent at 4 onto the light shielding film 45, an opening 46 (with the light shielding film removed, having a size of about 100 nm square) smaller than the wavelength of this beam is provided. Is formed.

The light (beam) propagating through the core 42 of the optical waveguide 41 and reflected by the reflection surface 44 depends on the propagation mode (single mode or multi-mode) in the optical waveguide 41, but from the reflection surface 44. At a relatively short propagation distance to the lower surface of the optical waveguide 41, it can be regarded as substantially parallel light (beam). Accordingly, the size of the reaching beam light substantially corresponds to the size of the core 42 of the optical waveguide 41, and at present,
From 0 μm square, it is considered to be relatively fine and about several μm square.

As described above, the size of the opening 46 is considerably smaller than the propagation wavelength of the waveguide 41, so that the propagating light that has reached just above the opening directly from the opening 46 directly from the lower surface of the waveguide. It does not propagate like ordinary light.
However, as is well known, even a minute aperture with a wavelength equal to or less than the wavelength, within a distance of a few tenths of a wavelength from the aperture (range within several 100 nm),
As shown in FIG. 5, a stationary light field (standing field) 55 that does not normally propagate is formed.

The standing light field 55 is disturbed by any scatterer entering the above range, and is scattered (propagated).
The light can propagate as light 56. For example, as shown in FIG. 5, a medium 10 having a high transmittance portion and a low transmittance portion on its surface (it is not always necessary to have irregularities on its surface) 10 is brought close to the stationary field within the existing distance. If this is done, the standing field light which has been disturbed by the medium itself and has become scattered light will pass only through the high transmittance portion of the medium, and the condensing lens 54 placed on the lower surface of the medium so as to face the present pickup.
And can be detected by the photodetector 53.

Therefore, if the digital information is recorded in such a manner that the high and low light transmittance portions of the medium correspond to some bit information, this information can be stored with a higher spatial resolution smaller than the light wavelength. It becomes possible to read.

The correspondence between the bit (0, 1) information and the actual physical characteristics of the medium is out of the scope of the present application, and therefore will not be described in detail, but the high transmittance portion and the low transmittance portion are set to 0 and 1, respectively. In addition to associating, the condition that the transmittance is the same and does not change (for example, the continuation of a high portion or the continuation of a low portion) is 0, while the transition from a high portion to a low portion or the transition from a low portion to a high portion is 1. Various associations such as association are possible.

At this time, by narrowing the light beam from the light source right above the minute aperture as small as possible, the light use efficiency can be increased, and the S / N ratio of the detected bit information can be improved. The optical waveguide has a property that light can be focused by gradually reducing the cross-sectional area of the core.

FIG. 6 shows an optical pickup according to a second embodiment of the present invention. Here, an example is shown in which the cross-sectional area of the core is gradually reduced from the other end to the one end of the optical waveguide. Show. That is, in the figure, 61 is a substantially rod-shaped optical waveguide having flexibility, 62 is a core of the optical waveguide 61, and the core 62 gradually reduces its width from the other end to one end of the optical waveguide 61. This gradually reduces the cross-sectional area. Reference numeral 63 denotes a clad surrounding the core 62, and reference numeral 64 denotes a reflection surface (a light-shielding film and minute openings are omitted).

As described above, by relatively increasing the cross-sectional area of the core 62 at the other end side of the optical waveguide 61, that is, at the incident side of the light source, the alignment of the light source or its condensing system with the optical axis of the core is facilitated. By taking a form in which the cross-sectional shape of the core 62 is narrowed down to one end side of the optical waveguide 61, the light use efficiency is increased,
The S / N ratio of bit information can be improved.

Here, in order to change the cross-sectional area of the core, there is a method of changing the width of the core, and also changing the height of the core or both of the width and the height of the core. Since it is very difficult to change the thickness (height) of each layer depending on the location in the individual layer, as shown in FIG. 6, it is necessary to keep the thickness of the layer constant and change the width to taper the cross-sectional shape. Realistic.

FIG. 7 shows a third embodiment of the optical pickup according to the present invention. Here, an example in which recording and reproduction can be performed using an optical waveguide having at least two cores is shown. That is, in the drawing, reference numeral 71 denotes a substantially rod-shaped optical waveguide having flexibility, and reference numerals 72 and 73 denote two optical waveguides formed on the optical waveguide 71.
This is a layer (two-channel) core. In this case, the lower layer (closer to the medium surface) core 72 is used for reproduction (detection), and the upper layer core 73 is used for recording. 74 is the core 7
Reference numeral 75 denotes a reflection surface, reference numeral 76 denotes a light shielding film, reference numeral 77 denotes a (fine) opening, reference numeral 78 denotes a concave portion, and reference numeral 79 denotes a condenser lens.

The reproduction operation has already been described with reference to FIGS. With respect to the recording operation, the laser path is the same as that for reproduction, and the recording laser light (pulse laser) that has propagated through the core 73 is reflected on the reflection surface 75 by the cladding 74.
Is reflected in the direction of transmission. Of course, it is necessary to remove the light-shielding film 76 at the portion of the clad surface where the recording light transmitted through the clad 74 has reached. However, since the beam diameter is the core size as it is, a small recording bit (optical characteristic It is difficult to form a dot portion that differs from its surroundings).

Therefore, for example, the reflection surface 7 of the optical waveguide 71
A portion where the recording light reflected by 5 reaches is etched with an ion beam or the like to form a recessed portion 78, and a material similar to the core or clad is deposited again by using a low directivity sputtering device. , Forming a convex lens-like body,
This can be used as the condenser lens 79.

The beam diameter of the recording light itself cannot be reduced sufficiently as long as a lens or a lens-like body is used. However, by adjusting the shape of the lens-like body, the light absorption characteristics of the medium, and the composition transition temperature, the lens diameter can be reduced. Fine recording bits can be formed by a high light intensity portion (tip) at the center of the beam spot narrowed by the shape.

In place of the lens-like body shown in this figure, spherical, hemispherical, and spheroidal transparent beads (having a different refractive index from the clad) shown in FIG. Of course, it is also possible to adopt a configuration in which a recording beam condensing lens function is provided.

It is desirable that the recording beam (condensed spot) and the standing field light for reproduction (detection) (small aperture) be aligned in the recording track direction (circumferential direction) as much as possible in line. The cores 72 and 73 (strictly in the axial direction) are arranged so as to be included in one plane, and the reflecting surface 75 is arranged so that the reflected light is included in the one plane.
Is provided. This makes it easy to always keep the recording beam (spot) on track immediately above the track, and allows the recorded bit to be confirmed immediately after recording by the detection beam, thereby improving the information transfer efficiency. Can also.

In the configuration shown in FIG. 7, the recording beam reflected by the reflecting surface 75 crosses the reproducing core 72. In the optical waveguide applied to the present invention, the refractive index difference between the core and the clad is obtained. And the influence of the beam traversing the core, such as reflection at the interface, is extremely small. The recording beam reflected by the reflecting surface 75 intersects with the reproduction beam (waveguide propagation), but since the intersection is orthogonal, the recording beam does not affect the reproduction beam.

FIG. 8 shows a fourth embodiment of the optical pickup of the present invention. In this embodiment, in the first embodiment, the clad at the portion where the light reflected by the reflection surface is transmitted is provided. Indicates an example in which spherical, hemispherical, spheroidal, or paraboloidal regions having different refractive indices are provided.

As already described with reference to FIG. 7, the light propagating through the core and reflected by the reflection surface has a size substantially equal to the shape of the core. Therefore, the core is finally narrowed down as close as possible to the reflecting surface, and projected as a narrow parallel emission light directly above the minute opening to increase the intensity of the standing field light for reproduction, and the detection light modulated by the medium Is an important and indispensable task for improving the S / N ratio of the sapphire.

Although a configuration in which the shape of the core is narrowed down is possible as already described with reference to FIG. It is also difficult to implement, for example, it is necessary to realize relative positioning with high accuracy.

In the present embodiment, for example, a spherical lens-like body 47 is put in the clad 43 at a portion where the light reflected by the reflection surface 44 is transmitted, and the light beam emitted from the relatively large core 42 is applied to this lens-like body. The minute opening 46 is formed using the body 47.
And the intensity of near-field light standing within a limited range from the opening 46 is increased as much as possible.

As for the lens-like body, there are parts which can be actually applied to desired dimensions, such as plastic beads of the order of μm. In addition, the present optical pickup can apply a manufacturing method in which a liquid plastic material is sequentially flown over a substrate as described later, and the liquid plastic material is cured and laminated.
By arranging and positioning beads at an appropriate position on the liquid clad and sequentially laminating the upper layers, a configuration can be made without causing optical distortion or the like around the lens-like body.

The lens-like body may be in the form of a sphere, a hemisphere, a paraboloid of revolution, a spheroid, or the like. However, it is needless to say that the lens-like body is not limited to this and cannot be expressed by an analytical function. Needless to say, a lens-like body having a complicated cross-sectional shape may be used.

FIG. 9 shows a fifth embodiment of the optical pickup according to the present invention. Here, an example in which a step portion is provided in the portion where the light shielding film is formed or in the vicinity of the opening in the first embodiment is shown. Is shown. That is, in the drawing, reference numeral 48 denotes a step portion (pad) having a stepped or inverted step shape (comb teeth or inverted comb teeth) toward one end of the optical waveguide. Is provided in the vicinity of the opening or the opening (the waveguide surface facing the medium (the sliding / floating running surface with the medium)).

As described with reference to FIG. 5, the present optical pickup presses one end of the optical waveguide against the medium by utilizing the elasticity of the optical waveguide, and opens the opening from the medium surface to a desired flying height (several tens nm to 10 nm).
(10 nm). If the waveguide surface provided with the opening has a simple planar configuration, one end (tip) of the optical waveguide may float too much due to the dynamic pressure effect of the air that rotates with the rotation of the medium. Also, when the pressing amount is increased to reduce the flying height, when the dynamic pressure effect of air cannot be sufficiently obtained, such as when starting and stopping the medium, the optical waveguide and the medium cause sliding wear, and This may cause damage to the recorded data and damage to the opening.

Therefore, by forming the pad 48 or the ABS surface as shown in FIG. 9, a substantially positive pressure (floating the optical pickup from the medium) is applied to the step portion and the land portion (convex portion) 48a of the pad. Further, a negative pressure (suction of the optical pickup to the medium surface) is generated in the reverse step portion and the groove portion (recess portion) 48b, and an ABS surface shape for appropriately arranging the magnitude and distribution of these forces is required. Thus, a floating clearance of a desired waveguide (opening) can be realized at an arbitrary traveling speed.

The dynamic pressure (positive pressure, negative pressure) generated at these steps is generated by the relative movement between the pickup and the medium. This configuration is also advantageous in that the pressing (contact) force of the contact can be reduced, and damage due to mutual contact sliding can be reduced.

FIG. 10 shows a sixth embodiment of the optical pickup of the present invention. In this embodiment, the optical waveguide described so far and a suspension for supporting a slider core of a floating head in a known magnetic disk drive are used. An example of a combination is shown.

That is, in the drawing, reference numeral 81 denotes a substantially rod-shaped optical waveguide having flexibility, and a distal end portion 82 on which the above-described reflecting surface, light-shielding film, and opening (all not shown) are formed.
9 has a stepped portion described with reference to FIG. 9, and has a structure in which it is gimbal-supported via a pair of thin leaf-shaped portions 84 at a joint 83 with a wide suspension. Reference numeral 91 denotes a suspension, and the optical waveguide 8
A rigid beam-shaped portion 92 which fixedly supports the first member 1 via its joint portion 83 and applies a pressing force, and a rigid base portion 93 which constitutes the fixed side of the pickup are formed of a soft leaf-shaped portion 94 having a spring property.
Are formed integrally with each other.

By adopting such a configuration, the optical waveguide 8
1 relaxes the mechanical requirements required for itself, for example, the rigidity is high in the in-plane direction, the bending rigidity and the torsional rigidity of the distal end portion 82 are reduced, and the allowable tolerance for setting the optical waveguide 81 to the medium is widened. be able to.

FIG. 11 is an exploded view of the configuration of FIG. 10 for easy understanding. Suspension 91
A circular boss (projection) 92 a is provided at the tip of the beam-shaped portion 92 of the optical waveguide 18.
A desired position of the ABS portion is pressed with a desired load (note that the boss 92a and the distal end portion 82 are not joined). It is preferable that the optical waveguide 81 be as thin and flexible as possible from the junction 83 with the suspension 91 to the root portion so as not to hinder the mechanical operation of the suspension 91. The root portion of the optical waveguide 81 is joined to a laser light source (not shown) via a connector 85 (in FIGS. 10 and 11, the surface close to the medium is illustrated as the upper side).

FIG. 12 shows an optical pickup according to a seventh embodiment of the present invention. In this embodiment, the light propagating in the core goes straight on the extension of the reflection surface at one end of the optical waveguide. An example is shown in which a second reflecting surface for returning at least a part of the generated light to the reflecting surface is formed. That is, in the figure, 101 is a substantially rod-shaped optical waveguide having flexibility, and 102 is an optical waveguide 10.
A core 103; a cladding 103 surrounding the core 102;
Is a reflection surface, 105 is a light shielding film, 106 is an opening, and 107 is a second reflection surface.

The optical waveguide 101 is temporarily moved to the core 102 on the way.
Is cut at an angle of 45 degrees with respect to the axial direction, and is coated with an appropriate reflective film or the like to form the reflective surface 104.
The reflecting surface 104 has a function of a beam splitter that reflects part of the light emitted from the light source and propagated in the core toward the opening 106, and transmits the rest as it is. In the optical waveguide 101, an optical waveguide portion similar to the above is joined on an extension of the reflection surface 104, and the end face of the extension is cut at an angle of 90 degrees with respect to the axial direction of the core 42. A second reflection surface 107 is formed by forming a phase shift film composed of a multilayer film and a reflection film.

Here, of the light emitted from the light source and reflected by the reflection surface 104 and directed to the opening 106, the opening 106
The portion that has not spilled out is reflected by the light shielding film 105 and returns to the reflection surface 104 again. Light that has passed through the reflecting surface 104 and travels straight reaches the second reflecting surface 107, is reflected there, and returns to the reflecting surface 104.

Next, the principle of detecting bit information of a medium according to the above configuration will be described.

First, under the condition that the standing field light standing in the minute aperture 106 does not interact with the medium 10 (scattering by the medium), the two return lights are reflected by the reflection surface 104, and their intensities are equal in phase. Is adjusted so that is completely anti-phase. Specifically, the second reflection surface 1
By changing the thickness of the multilayer film constituting the layer 07 and the reflectivity of the outermost reflective film, the phase and intensity of the return light from the second reflective surface 107 can be changed. These two return lights interfere with each other on the reflection surface 104, and if the above condition is ideally satisfied, the return light returns to the core 102 of the optical waveguide 101 in the opposite direction, and the intensity of the return (interference) light becomes zero. .

Next, when the opening 106 floats on the medium on which the information is transferred, for example, in an uneven shape, the protrusion (land)
Immediately above, the standing field light oozing out of the opening 106 like a brush tip interacts with the medium, and becomes scattered (propagated) light to dissipate the light energy. In the concave portion (groove portion), the standing field light from the opening portion 106 is not scattered and does not dissipate in energy.

This is because the return light returning from the opening 106 to the reflection surface 104 indicates that when the opening 106 comes over the land portion and the groove portion of the medium 10, the standing field light The intensity of the return light varies slightly depending on the presence or absence of the dissipation. That is, the return light from the opening 106 is superimposed on a constant DC light by the unevenness (groove / land) of the medium 10 and is subjected to delicate intensity modulation.

By the way, the return light from the second reflection surface 107 is set so as to cancel a certain DC light of the return light from the opening 106 as previously adjusted. The intensity fluctuation of the interference light returning from the surface 104 via the core 102 of the optical waveguide 101 directly reflects the degree of scattering / non-scattering of the standing field light that seeps out of the opening 106. .

Of course, it is also possible in principle to directly photoelectrically convert the return light from the opening 106 including the DC component and cancel the DC component in the converted electric signal. However, since the amount of modulation of the return light from the opening is very small, the modulation itself is buried in the intensity fluctuation of the light source and the electrical noise at the time of photoelectric conversion, and it is necessary to detect with a desired S / N ratio. Is very difficult.

When the light from the same light source is partially branched and used as reference (cancel) light as in this embodiment, the influence of the fluctuation of the light source itself can be eliminated. Furthermore, there is no large DC light component at the time of the photoelectric conversion of the return (interference) light, and ideally only the AC component. Therefore, there is an advantage that a very wide dynamic range is not required for the converter (photodetector). is there. Further, in this embodiment, it is not necessary to provide a photodetection system below the medium, and one-sided access is possible.

The light generation / detection system of the waveguide shown in FIG.
A light source 51, condenser lenses 52 and 54, a photodetector 53, a polarizing beam splitter 57, a wavelength plate 58, and the like are provided. Most of the light emitted from the light source 51 is the core 1 of the optical waveguide 101.
The return light, which is incident on the optical waveguide 02 and interferes with one end of the optical waveguide 101, is reflected upward in the drawing by the polarization beam splitter 57 and is incident on the photodetector 53.

In general, an advantage of the optical information storage device is that high-speed and high-bandwidth tracking control can be performed with very high accuracy only by swinging a recording laser beam by a small angle using a galvanometer mirror or the like. In the cantilever foil type optical pickup as in the present application, the light propagating through the core cannot be swung by the optical lever method.

FIG. 13 shows an eighth embodiment of the optical pickup according to the present invention. In this embodiment, a notch is formed in a part of the cladding of the optical waveguide, and a solid displacement element is joined to the notch. An example is shown in which tracking control is performed by using this method. That is, in the drawing, 49a and 49b are notches provided on both sides of the core 42 of the clad 43 near one end of the optical waveguide 41, and make the optical waveguide 41 easily elastically deform in the direction around the axis of the core 42. ing. Also, 111, 112
Is a solid displacement element such as a piezoelectric element, a magnetostrictive element, or an electrostatic displacement element (an element that performs minute displacement according to an applied voltage), which is joined to the clad 43 so as to straddle the notches 49a and 49b.

Here, this is extended to each of the elements 111 and 112, for example, to the element 112 on the left side of the core 42,
By applying a signal voltage or the like that reduces this to the right element 111, one end of the optical waveguide 41 can be displaced to the right and its opening (not shown) can be slightly moved right. In addition, if a signal voltage or the like opposite to the above is applied, the opening can be slightly moved to the left, and the micro tracking as described above can be performed.

In this embodiment, the solid displacement element is joined to the cutout portion later. However, the present invention is not limited to this configuration. For example, the solid displacement element may be directly buried when forming an optical waveguide (cladding). Of course you can take.

Next, although not an embodiment of the present application, a manufacturing method will be described with reference to FIG. 14 to show that the optical pickup of the present invention can be realized.

First, a Si substrate 121 or the like can be used as a substrate on which an optical waveguide structure is based.

In general, a free surface obtained by hardening a liquid material and hardening has a surface roughness, undulation, twist, and the like, and the flatness and smoothness of the surface are not sufficient. It is very inadequate to position the opening on the media up to the gap. Since a very smooth and flat surface can be obtained from Si, a liquid plastic multilayer film is formed on the substrate, and the flat shape of the Si substrate 121 is kept as it is by peeling off the Si substrate 121 in the final step. It can be transferred to the medium facing surface of the waveguide.

When the desired thickness of the optical waveguide is small and curling or the like occurs in the optical waveguide when the Si substrate is peeled, the residual stress is applied to the optical waveguide by etching and removing the Si substrate itself with an etching solution. A formation method that does not occur can be applied. Also, regarding the ABS surface, it is not always necessary to form a stepped portion on the surface of the optical waveguide once formed by sputtering, etching or the like, and as shown in FIG. May be formed by etching or the like, and a cladding layer and a core layer may be sequentially formed thereon.

As described above, the propagation light of the core bent at the reflection surface generally has a large beam width, and therefore needs to be sufficiently condensed immediately above the opening from the viewpoint of improving light use efficiency. Since each layer of the optical waveguide is sequentially coated with a liquid plastic and cured and laminated, as shown in FIGS. 4B and 4C, when the clad material 122 is applied halfway, the clad material is placed at the position where the opening is formed. A microlens can be easily formed by placing a bead-shaped lens-like body 123 having a different refractive index from that of the lens-like body 122 and filling the periphery thereof with a cladding material 122 and solidifying the same. In addition, residual stress when the lens-like body 123 is embedded is reduced. Will not remain.

Thereafter, a core material 124 is applied as shown in FIG. 9D, a cladding material 122 is applied again as shown in FIG. 8E, and a Si substrate is applied as shown in FIG. Peeled from 121 and one end is 4
If the reflective surface 125 is formed by cutting at an angle of 5 degrees, the process is completed.

As described above, regarding the structure of the lens-like body, a cylindrical hole is formed in the clad portion of the optical waveguide, and the lens material is formed on the hole by low-directivity sputtering. There is a way to do that. For this purpose, Si
What is necessary is just to form a cylindrical convex portion on the substrate and transfer this to the clad. There is also a method of forming a pseudo-spherical concave shape corresponding to a female type corresponding to a lens on the Si substrate itself, and transferring this to the clad.

[0088]

As described above, according to the present invention, according to the present invention, a flexible, substantially rod-shaped optical waveguide having a core and a clad is used, and the light propagates through the core to one end thereof. By providing a reflecting surface that reflects at least a part of the light in a direction transmitting the clad, the optical path of the propagating light in the core is bent, and a light-shielding film is provided at a portion where the propagating light passes through the clad and exits. The provision of the minute opening smaller than the wavelength of the light to be used makes it possible to realize an optical pickup capable of detecting (reproducing) recorded information on a medium with high spatial resolution with a very simple configuration.

Further, in the above optical pickup, since the cross-sectional area of the core is formed so as to gradually decrease from the other end to the one end of the optical waveguide, the incident beam is formed immediately above the minute opening. It is possible to obtain a reproduced signal that is efficiently stopped down, has high light use efficiency, and has a high S / N ratio.

Further, in the above optical pickup, a spherical, hemispherical, spheroidal, or paraboloid of revolution having a different refractive index from the cladding in a portion where the light reflected by the reflecting surface is transmitted. Since the region is provided, similarly, the incident beam is efficiently narrowed immediately above the minute opening, and a reproduced signal having a high light use efficiency and a high S / N ratio can be obtained.

Further, in the above optical pickup, an optical waveguide having at least two cores is used, and reflected light of light propagating in each of the at least two cores is on one straight line substantially coincident with the longitudinal direction of the optical waveguide. , An optical pickup capable of recording information can be realized with a simple configuration.

Further, in the above optical pickup, an optical waveguide having at least two cores is used, and reflected light of light propagating in each of the at least two cores is on one straight line substantially coincident with the longitudinal direction of the optical waveguide. A concave portion is provided on the clad surface where the reflected light is transmitted, and a lens with a convex cross section is formed in the concave portion. Can be realized.

Further, in the above optical pickup, a stepped portion having a stepped shape or an inverted stepped shape toward one end of the optical waveguide is provided near the portion where the light shielding film is formed or in the vicinity of the opening. It is possible to realize an optical pickup with a simple configuration that can relax the set tolerance and that has excellent floating stability.

In the above optical pickup, the rigid beam-shaped portion for supporting the optical waveguide and the rigid base constituting the fixed side of the pickup are integrally formed with a soft leaf-shaped portion having spring property interposed therebetween. In addition to using the suspension formed on the optical waveguide, the optical waveguide is provided with a joint portion with the beam-shaped portion of the suspension, and the suspension is elastically supported at a portion where the light shielding film is formed at one end of the main body. An optical pickup having excellent stability and high in-plane support rigidity and capable of high-speed track seeking can be realized with a simple configuration.

Further, in the above-mentioned optical pickup, at least a part of the light propagating straight through the reflecting surface among the light propagating in the core is returned to the reflecting surface on the extension of the reflecting surface on one end side of the optical waveguide. Since the reflection surface is formed, an optical pickup that can access the medium on one side can be realized with a simple configuration.

Finally, in the above optical pickup, a notch is formed in a part of the cladding of the optical waveguide, and a solid displacement element is joined to the notch, so that an optical pickup capable of high-speed microtracking can be simplified. The effect is extremely large, for example, the structure can be realized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an example of a conventional optical pickup.

FIG. 2 is a configuration diagram showing another example of a conventional optical pickup.

FIG. 3 is a configuration diagram showing still another example of the conventional optical pickup.

FIG. 4 is a configuration diagram showing a first embodiment of the optical pickup of the present invention.

FIG. 5 is a diagram showing the operation principle of the optical pickup of the present invention.

FIG. 6 is a configuration diagram showing a second embodiment of the optical pickup of the present invention.

FIG. 7 is a configuration diagram showing a third embodiment of the optical pickup of the present invention.

FIG. 8 is a configuration diagram showing a fourth embodiment of the optical pickup of the present invention.

FIG. 9 is a configuration diagram showing a fifth embodiment of the optical pickup of the present invention.

FIG. 10 is a configuration diagram showing a sixth embodiment of the optical pickup of the present invention.

FIG. 11 is a diagram for explaining the configuration of the optical pickup of FIG. 10 in detail;

FIG. 12 is a configuration diagram showing a seventh embodiment of the optical pickup of the present invention.

FIG. 13 is a configuration diagram showing an optical pickup according to an eighth embodiment of the present invention.

FIG. 14 illustrates a method for manufacturing an optical pickup of the present invention.

[Explanation of symbols]

10: optical storage medium, 11: recording layer of optical storage medium, 41,
61, 71, 81, 101: optical waveguide, 42, 62, 7
2, 73, 102: core, 43, 63, 74, 103:
Cladding, 44, 64, 75, 104: reflective surface, 45,
76, 105: light shielding film, 46, 77, 106: minute opening, 47: lens-like body, 48: step, 49a, 49
b: notch, 51: light source, 52, 54: condenser lens,
53: photodetector, 55: near-field light, 56: scattered light, 57: polarizing beam splitter, 58: wave plate, 7
8: concave portion, 79: condenser lens, 91: suspension, 107: second reflection surface, 111, 112: solid displacement element.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Yoshiaki Kurokawa, Inventor 3-19-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Japan Telegraph and Telephone Corporation (72) Inventor Yasuko Ando 3-192-1, Nishi-Shinjuku, Shinjuku-ku, Tokyo No. F-term in Japan Telegraph and Telephone Corporation (reference) 2H050 AC01 AC03 AC83 AC87 AC90 5D119 AA10 AA11 AA43 BA01 CA06 JA35 JA36 JA40 JA60 JA64 MA06

Claims (9)

[Claims] 1. An optical pickup in an optical information storage device using near-field light, comprising: a substantially rod-shaped flexible optical waveguide having a core and a clad; and one end side of the optical waveguide. A reflecting surface that reflects at least a portion of light propagating in the core in a direction that transmits the cladding; and a light transmission formed on a cladding surface centered on a portion through which the light reflected by the reflecting surface transmits. An optical pickup comprising: a light-shielding film that blocks light; and an opening formed at a portion through which light reflected by the reflection surface is transmitted and smaller than a wavelength of light to be used. 2. The optical pickup according to claim 1, wherein a cross-sectional area of the core is gradually reduced from the other end to the one end of the optical waveguide. 3. A spherical, hemispherical, spheroidal, or paraboloidal region having a different refractive index from the cladding is provided in a portion of the cladding where light reflected by the reflecting surface is transmitted. The optical pickup according to claim 1, wherein: 4. An optical waveguide having at least two cores is used, and reflected light of light propagating in each of the at least two cores is arranged on one straight line substantially coinciding with a longitudinal direction of the optical waveguide. The optical pickup according to claim 1, wherein the optical pickup is configured as follows. 5. A concave portion is provided on a clad surface centered on a portion through which light reflected by the reflecting surface is transmitted, and a lens having a convex cross section is formed in the concave portion. Optical pickup. 6. The step according to claim 1, wherein a stepped portion having a stepped shape or an inverted stepped shape toward one end of the optical waveguide is provided in a portion where the light shielding film is formed or in the vicinity of the opening. Optical pickup. 7. A rigid beam-shaped portion for supporting an optical waveguide and a rigid base constituting a fixed side of the pickup are integrally formed with a soft leaf-shaped portion having spring property interposed therebetween. 2. The light according to claim 1, wherein a suspension is used, and a joint portion with a beam-shaped portion of the suspension is provided in the optical waveguide, and the portion where the light shielding film is formed at one end of the main body is elastically supported by the suspension. pick up. 8. A second reflecting surface is formed on an extension of the reflecting surface on one end side of the optical waveguide to return at least a part of light propagating straight through the reflecting surface among the light propagating in the core to the reflecting surface. The optical pickup according to claim 1, wherein: 9. The optical pickup according to claim 1, wherein a notch is formed in a part of a clad of the optical waveguide, and a solid displacement element is joined to the notch.