JP4397864B2 - RECORDING / REPRODUCING APPARATUS AND METHOD FOR CONTROLLING LIGHT RADIATION POSITION - Google Patents

Description

  The present invention relates to a recording / reproducing apparatus for recording / reproducing information using light and a magnetic field, and a method for controlling a light irradiation position in the recording / reproducing apparatus.

Currently, various research and development have been conducted with the aim of increasing the capacity of optical recording media, magnetic recording media, and recording / reproducing apparatuses using these as recording media. Among these, the optically assisted magnetic recording system is attracting attention as a next-generation high-density magnetic recording system. This technique performs magnetic recording on a magnetic recording medium having a high coercive force that is resistant to thermal fluctuations, and can achieve a magnetic recording density exceeding 100 Gb / in ² .

  Specifically, when the light is focused on the surface of the magnetic recording medium and the temperature of the magnetic recording medium is locally increased, the coercive force of the magnetic recording medium is reduced at the portion where the temperature is increased. Magnetic recording by a magnetic head is possible.

In such a system, it is necessary to align the position of the light irradiation unit and the recording head. For example, Patent Document 1 discloses a method for that purpose. Further, in order to achieve higher density magnetic recording, it is necessary to make the focused spot size smaller. In recent years, techniques using near-field light exceeding the diffraction limit of light have been proposed. For example, in the technique of Patent Document 2, a floating head having a minute aperture for generating near-field light and a recording / reproducing coil around it, and an optical head having an objective lens for irradiating the minute aperture with light are provided. A recording / reproducing apparatus provided has been proposed.
JP 2000-242988 (released September 8, 2000) JP 2000-57622 (released February 25, 2000)

  The apparatus described in Patent Document 1 has a configuration in which an optical pickup is disposed on one side in a direction facing the disk and a magnetic head is disposed on the other side. In this case, in order to focus the light from the optical pickup on the magnetic film, it is necessary to irradiate the light through the disk. However, in such a configuration, if the focused spot size is reduced to achieve high-density recording, there is a possibility that the local temperature rise cannot be sufficiently performed due to the aberration of the beam spot due to the thickness or tilt of the disk. Recording characteristics will deteriorate.

  Therefore, in order to eliminate the influence of the thickness and tilt of the disk, the optical pickup and the magnetic field are not directly incident on the recording layer formed on one surface of the disk substrate, but rather incident on the disk substrate. A configuration has been proposed in which the head is disposed on the side facing the recording layer.

  As such an example, the above-mentioned Patent Document 2 is raised. In this patent document 2, near-field light is further generated during recording. As described above, when near-field light is generated, it is necessary to accurately control the positional relationship between the light irradiation portion and the minute opening. For example, even when a laser beam having a wavelength of 640 nm and an objective lens having an NA of 0.65 are used, the spot diameter of the light irradiation part is as small as about 1 μm. Further, since the minute aperture is naturally smaller than the spot diameter, the positional relationship between the minute aperture and the light irradiating unit needs to be precisely controlled on the order of submicrons. However, even if Patent Document 2 describes a method for controlling the gap between the flying head (recording head) and the optical recording medium, the positional relationship between the minute aperture on the flying head and the optical head, that is, the light irradiation position, is described. It does not describe how to control.

  Accordingly, an object of the present invention is to provide a recording / reproducing apparatus capable of accurately controlling the positional relationship between the recording head and the light irradiation position from the optical head, and a method for controlling the light irradiation position in the recording / reproducing apparatus. .

  In order to solve the above-described problems, the recording / reproducing apparatus of the present invention includes an optical head that collects and emits light emitted from a light source, and a magnetic field generated from the conductor by passing a current through the conductor. A recording / reproducing apparatus that records information on an information recording medium by irradiating the conductor with light from the optical head, the irradiation position of the light from the optical head And at least one of reflected light from the conductor portion of the recording head and reflected light from the information recording medium with respect to the light emitted from the optical head. A detection unit that generates a detection signal based on the detection signal, a determination unit that determines an irradiation position of light from the optical head based on the detection signal, and the optical head based on a determination result of the determination unit. The irradiation position of the light and the position of the conductor portion is characterized in that a control means for controlling said moving means to match.

  Further, the method for controlling the light irradiation position in the recording / reproducing apparatus of the present invention comprises: an optical head that collects and emits light emitted from a light source; and a magnetic field generated from the conductor by passing a current through the conductor. A recording head for applying to an information recording medium, irradiating light from the optical head to the conductor portion, and controlling the light irradiation position in a recording / reproducing apparatus for recording information on the information recording medium, Generating a detection signal based on at least one of reflected light from the conductor of the recording head and reflected light from the information recording medium for the light emitted from the optical head; and based on the detection signal Determining the irradiation position of the light from the optical head, and based on the determination result, the irradiation position of the light from the optical head and the position of the conductor portion are matched to each other. It is characterized by comprising the step of relatively moving the irradiation position of the light from the optical head and the position of the recording head.

  According to the above configuration, the light emitted from the optical head toward the recording head is applied to the conductor portion of the recording head, or is applied to the information recording medium off the conductor portion. A detection signal is obtained from reflected light from the conductor portion of the recording head and / or reflected light from the information recording medium, or at least one of them. In this case, since different detection signals are obtained from these reflected lights, the irradiation position of the light from the optical head can be determined based on the detection signals. Therefore, based on this determination result, the light irradiation position from the optical head and the position of the conductor portion can be matched by relatively moving the light irradiation position from the optical head and the recording head position. . That is, the positional relationship between the recording head and the irradiation position of light from the optical head can be accurately controlled.

  In the determination of the light irradiation position, for example, the light irradiation position can be determined by measuring the shape of the conductor portion by reading the change in the detection signal. Alternatively, if the shape including the dimensions of the conductor part and the detection signal at each part of the conductor part are recognized in advance, based on the prior recognition information and the actually obtained detection signal (for example, recognized in advance). The light irradiation position can be determined by comparing the length of each portion of the conductor portion with the measured length of the conductor portion.

  The recording / reproducing apparatus of the present invention applies an electric current to an optical head for condensing and irradiating light emitted from a light source and a conductor having a constriction, and applies a magnetic field generated from the constriction to an information recording medium. A recording / reproducing apparatus that irradiates light from the optical head onto the constricted portion and records information on an information recording medium, the irradiation position of the light from the optical head and the recording head A detection signal based on at least one of a reflected light from the conductor of the recording head and a reflected light from the information recording medium for the light emitted from the optical head and the moving means for relatively moving the position. A detecting means for generating; a determining means for determining an irradiation position of light from the optical head based on the detection signal; and an irradiation position of the light from the optical head based on a determination result of the determining means. The position of the constriction of the conductor portion is characterized in that a control means for controlling said moving means so as to match the.

  The method for controlling the light irradiation position in the recording / reproducing apparatus of the present invention is generated from the constricted portion by passing an electric current through an optical head that collects and emits the light emitted from the light source and a conductor portion having the constricted portion. A recording head that applies a magnetic field to an information recording medium, irradiates light from the optical head onto the conductor, and controls the light irradiation position in a recording / reproducing apparatus that records information on the information recording medium. Generating a detection signal based on at least one of reflected light from the conductor of the recording head and reflected light from the information recording medium for the light emitted from the optical head; and Determining the irradiation position of the light from the optical head based on the result, and matching the irradiation position of the light from the optical head with the position of the constriction portion of the conductor based on the determination result. As to, it is characterized by comprising a step of relatively moving the position of the recording head and the irradiation position of the light from the optical head.

  According to the above configuration, the light emitted from the optical head toward the recording head is applied to the conductor portion of the recording head, or is applied to the information recording medium off the conductor portion. A detection signal is obtained from reflected light from the conductor portion of the recording head and / or reflected light from the information recording medium, or at least one of them. In this case, since different detection signals are obtained from each of the reflected lights, the irradiation position of the light from the optical head can be determined based on the detection signals. Therefore, based on this determination result, the irradiation position of the light from the optical head and the position of the recording head are moved relative to each other so that the irradiation position of the light from the optical head matches the position of the constriction portion in the conductor portion. be able to. That is, the positional relationship between the recording head and the irradiation position of light from the optical head can be accurately controlled. The determination of the light irradiation position can be performed in the same manner, for example, by the above method.

  Moreover, in the structure of this invention, the irradiation position of light is made to correspond with the position of the constriction part of a conductor part. Therefore, recording on the information recording medium uses light leaked from the narrowed portion. Since the diameter of the leaked light is reduced by the narrowed portion, high density recording can be performed. Furthermore, since near-field light can be generated from the narrowed portion, higher density recording can be performed. Therefore, according to this, precise position control of light is possible and high-density recording is possible.

  In the recording / reproducing apparatus, the determination unit may determine a light irradiation position based on an amplitude of a detection signal detected from the conductor part and an amplitude of a detection signal detected from the information recording medium. Good.

  Further, the light irradiation position control method in the recording / reproducing apparatus described above is based on the light irradiation position based on the amplitude of the detection signal detected from the conductor and the amplitude of the detection signal detected from the information recording medium. It is good also as a structure to determine.

  According to the above configuration, when the reflectance of the conductor portion of the recording head and the reflectance of the information recording medium are different, the amplitude of the detection signal detected from the reflected light of the conductor portion and the reflected light of the information recording medium The detected signal has a different amplitude. Therefore, since the change in the detection signal can be read by detecting this difference in amplitude, it is possible to determine the light irradiation position. In this case, it is preferable to recognize the shape of the conductor portion in advance. According to this, the irradiation position of light can be easily determined by comparing the previously recognized information with the actual change in the detection signal.

  In the recording / reproducing apparatus, the determination unit determines the light irradiation position based on at least one of a shape of a detection signal detected from the conductor part and a shape of a detection signal detected from the information recording medium. It is good also as composition to do.

  Further, the method for controlling the light irradiation position in the recording / reproducing apparatus described above is characterized in that the light irradiation position is determined by at least the shape of the detection signal detected from the conductor part and the shape of the detection signal detected from the information recording medium. It is good also as a structure determined based on one side.

  According to the above configuration, when the reflectance of the conductor portion of the recording head and the reflectance of the information recording medium are different, the shape of the detection signal detected from the reflected light of the conductor portion and the reflected light of the information recording medium The detected signal is different in shape. Therefore, since the change in the detection signal can be read by detecting the difference in the shape of the detection signal, the irradiation position of the light can be determined. In this case, it is preferable to recognize the shape of the conductor portion in advance. According to this, the irradiation position of light can be easily determined by comparing the previously recognized information with the actual change in the detection signal.

  For example, even when only the detection signal of the conductor part or the information recording medium is obtained and the amplitude difference cannot be detected, the irradiation position of the light can be determined based on the shape of the detection signal. Therefore, in such a configuration, the light irradiation position can be accurately controlled.

  In the recording / reproducing apparatus, the reflectance of the reflected light may be higher in the reflectance of the conductor portion than the reflectance of the information recording medium.

  In the method for controlling the light irradiation position in the recording / reproducing apparatus, the reflectance of the reflected light may be higher in the reflectance of the conductor portion than that of the information recording medium.

  According to the above configuration, since the detection signal detected from the conductor portion of the recording head is larger than the detection signal detected from the information recording medium, the shape of the conductor portion can be detected more accurately. is there. Therefore, the positional relationship between the recording head and the irradiation position of light from the optical head can be accurately controlled.

  In the recording / reproducing apparatus, the narrowed portion may be configured to be smaller than the diameter of the light spot from the optical head that is irradiated to the narrowed portion.

  In the method for controlling the light irradiation position in the recording / reproducing apparatus, the narrowed portion may be configured to be smaller than the diameter of the light spot from the optical head irradiated to the narrowed portion.

  According to the above configuration, since the constriction is within the spot diameter, the shape of the constriction can be recognized more accurately. In addition, since the light spot can be miniaturized by the narrowed portion, that is, the light irradiated to the information recording medium becomes leakage light from the narrowed portion, so that a smaller recording mark can be recorded and the recording density is improved. Can be made.

  In the recording / reproducing apparatus, the recording head may include a near-field generating element that generates a near field from the narrowed portion.

  In the above configuration, the near field exists only in a region below the wavelength of light. Therefore, according to the above configuration, since recording is performed on the information recording medium by the near field, higher density recording can be performed.

  In the recording / reproducing apparatus, the detection unit includes a light receiving element that receives the reflected light and performs photoelectric conversion, the light receiving element includes a light receiving surface divided into a plurality of parts, and the determination unit includes the detection unit. The irradiation position of the light from the optical head may be determined based on the amplitude of the detection signal from each light receiving surface divided in the moving direction of the reflected light in the means.

  The method of controlling the light irradiation position in the recording / reproducing apparatus uses a light receiving element that has a plurality of light receiving surfaces and performs photoelectric conversion, and from each light receiving surface divided in the moving direction of the reflected light in the light receiving element. It may be configured to determine the irradiation position of light from the optical head based on the amplitude of the detection signal.

  According to said structure, since the irradiation position of the light from the said optical head is determined based on the amplitude of the detection signal from each light-receiving surface divided | segmented in the moving direction of the said reflected light in a light receiving element, a conductor part and information The boundary with the recording medium can be accurately detected. Thereby, the irradiation position of light can be more accurately controlled by the detection signal from the light receiving element.

  In the recording / reproducing apparatus, the light receiving element may have a light receiving surface divided into four parts.

  In the recording / reproducing apparatus, the determination unit includes a set of two light receiving surfaces arranged in a direction orthogonal to the direction of movement of the received reflected light with respect to the four light receiving surfaces of the light receiving element in the detecting unit. In this case, the irradiation position of the light from the optical head may be determined based on the amplitude of the detection signal from the light received by the light receiving surfaces of these sets.

  Further, in the method of controlling the light irradiation position in the recording / reproducing apparatus, the light receiving surface of the light receiving element is divided into four parts, and the four light receiving surfaces of the light receiving element are moved with respect to the direction of movement of the received reflected light. The two light receiving surfaces arranged in the orthogonal direction are organized into two sets, and the irradiation position of the light from the optical head based on the amplitude of the detection signal from the light received by each set of the light receiving surfaces It is good also as a structure which determines.

  According to the above configuration, for the four light receiving surfaces of the light receiving element, two light receiving surfaces arranged in a direction perpendicular to the direction of movement of the received reflected light are knitted into two sets, The irradiation position of light from the optical head is determined based on the amplitude of the detection signal from the light received by the pair of light receiving surfaces. Therefore, the light irradiation position can be accurately controlled. Moreover, even when the moving direction of the reflected light changes in a direction orthogonal to the previous direction, the light irradiation position can be accurately controlled based on the detection signal from the light receiving element.

  In the recording / reproducing apparatus, the conductor portion has a plurality of edge portions extending in directions orthogonal to each other, and the control means includes a direction in which the irradiation position of the light is orthogonal to the direction of the edge portion of the conductor portion, and The moving means is controlled to move in parallel directions, and the light receiving element of the detecting means is one of the two directions that are the directions of movement of the reflected light accompanying the movement of the irradiation position of the light in the two directions. It is good also as a structure which has the light-receiving surface divided | segmented into the direction parallel to at least one direction.

  According to the above configuration, the direction of the edge portion of the conductor portion, the moving direction of the light irradiation position, and the arrangement direction of the dividing surface of the light receiving element are defined, so that the light irradiation position can be controlled more accurately. Can do.

  As described above, the recording / reproducing apparatus of the present invention includes at least the moving means and the reflected light from the conductor portion of the recording head and the reflected light from the information recording medium for the light emitted from the optical head. Detection means for generating a detection signal based on one side, determination means for determining an irradiation position of light from the optical head based on the detection signal, and from the optical head based on a determination result of the determination means It is the structure provided with the control means which controls the said moving means so that the irradiation position of light and the position of the said conductor part may correspond.

  Thereby, the irradiation position of the light irradiated from the optical head can be precisely matched with the conductor part that generates the recording magnetic field in the recording head. Further, in the configuration having the narrowed portion in the conductor portion, high density recording is possible.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. In the embodiment described below, a magnetic disk of an optically assisted magnetic recording system is used as the information recording medium.

[Embodiment 1]
FIG. 1 is a schematic diagram for explaining a recording / reproducing apparatus using a recording head according to the present embodiment. In the drawing, reference numeral 1 denotes a light-transmitting substrate, and 2 denotes a conductor layer having a narrowed portion 12 (see FIGS. 4A and 4B). The substrate 1 and the conductor layer 2 are constituent elements of the recording head 3.

  The conductor layer 2 does not have to be provided on the entire lower surface of the substrate 1, and may be provided on a part of the lower surface of the substrate 1. The recording head 3 is provided with wiring (not shown) for applying a current to the conductor layer 2.

  Further, in FIG. 1, reference numeral 4 denotes a light source, and 5 denotes an objective lens for condensing the light from the light source 4 on the narrowed portion 12 of the conductor layer 2. These light source 4 and objective lens 5 constitute an optical head 6. The optical head 6 incorporates a drive unit (not shown) for moving the objective lens 5 and condensing it on the conductor layer 2.

  Further, in FIG. 1, reference numeral 7 denotes an information recording medium. The information recording medium 7 includes, for example, a TbFeCo magnetic layer, a dielectric layer, a protective film made of carbon, and a lubricating layer for ensuring lubricity between the recording head 3 and the information recording medium 7 on a disk-shaped substrate. And the like are stacked in this order, and the reflectance is about 45%.

  The recording head 3 is attached to a suspension (not shown) and floats by an air flow generated by the rotation of the information recording medium 7. The distance between the recording head 3 and the information recording medium 7 is about 1 μm or less, preferably 10 nm or less.

  More specifically, the optical head 6 has a configuration shown in FIG. 2, for example. As described above, 4 indicates a light source and 5 indicates an objective lens. A collimating lens 30 shapes the light emitted from the light source 4. Reference numeral 31 denotes a beam splitter. Light is condensed by the objective lens 5 via the beam splitter 31 and irradiated to the vicinity of the conductor layer 2 (constriction portion 12) of the recording head 3. The reflected light of the irradiated light is detected by the photodiode 14 via the beam splitter 31 and the condenser lens 32. When a two-divided photodiode is used as the photodiode 14, the shape including the size of the conductor layer 2 can be detected, and the positional relationship between the light irradiation position and the conductor layer 2 can be accurately controlled.

  Furthermore, in FIG. 1, 8 is a position control part. The position control unit 8 analyzes the reflected light of the light irradiated from the optical head 6 to the vicinity of the narrowed portion 12 of the conductor layer 2, and based on the position information obtained from the analysis result, the light irradiation position by the light source 4 And a control signal for controlling the relative position between the recording head 3 and the information recording head 3 are output to the head drive unit 9. The position control unit 8 is made to recognize the shape of the conductor layer 2 in advance.

  The configuration of the position control unit 8 will be described in more detail. FIG. 3 shows a block diagram of the position control unit 8. The position control unit 8 includes a detection unit 40 that generates a detection signal from reflected light detected by the photodiode 14 as illustrated, a determination unit 41 that determines the irradiation position of light on the conductor layer 2 from the detection signal, and the Based on the determination result by the determination unit 41, a control unit 42 is provided to control the light irradiation position and the position of the conductor layer 2 to coincide with each other.

  The detection unit 40 demodulates the reflected light into an electrical signal and generates a detection signal. At this time, for example, when the reflectance of the conductor layer 2 is higher than the reflectance of the information recording medium 7, the detection signal obtained from the conductor layer 2 has a larger signal amplitude than the detection signal obtained from the information recording medium 7. Signal.

  In the determination unit 41, the amplitude of the detection signal obtained from the conductor layer 2, the amplitude of the detection signal obtained from the information recording medium 7, and the amplitude of the detection signal obtained from the boundary between the conductor layer 2 and the information recording medium 7, In addition, information such as the shape of the conductor layer 2 is given in advance. As information on the shape of the conductor layer 2, dimensions such as X1, X2, Y1, Y2, Y3, and Y4 of the conductor layer 2 in FIG. 4 as described later are given. Therefore, in the determination unit 41, since the amplitude of the detection signal from the conductor layer 2 and the amplitude of the detection signal from the information recording medium 7 are different, the light irradiation position is set by setting the threshold value to a certain amplitude value. Whether it is on the conductor layer 2 or the information recording medium 7 can be determined. Further, by measuring the amount of movement when the recording head 3 is moved using the head drive unit 9 and comparing the amount of movement with the dimensions of the conductor layer 2, the light irradiation position is determined more precisely. can do.

  The control unit 42 outputs a control signal to the head driving unit 9 based on the determination result obtained from the determination unit 41, and controls the moving direction and moving amount of the recording head 3 by the head driving unit 9.

  The head drive unit 9 moves the recording head 3 in order to control the relative position between the light irradiation position by the light source 4 and the information recording head 3 based on the control signal from the position control unit 8. The head drive unit 9 is composed of a piezo element, for example. When a piezo element is used, the recording head 3 can be moved within a range of ± 50 μm, and a positioning accuracy in units of 10 nm can be obtained substantially. Reference numeral 10 denotes light leaked from the narrowed portion 12 of the conductor layer 2.

  That is, the light irradiation position is determined by the determination unit 41 from the detection signal obtained by the detection unit 40, and the operation of the head drive unit 9 is controlled by the control unit 42. By repeating this operation, it is possible to finally move the light irradiation position to a predetermined position of the conductor layer 2, for example, the narrowed portion 12.

  4A and 4B are detailed schematic views of the recording head 3. FIG. FIG. 4A is a front view when the recording head 3 is viewed from the side facing the information recording medium 7. A conductor layer 2 having a narrowed portion 12 is formed on the surface of the information recording head 3 facing the information recording medium 7. The conductor layer 2 is made of Au in the present embodiment, but is not limited thereto, and may be formed of a metal having high electrical conductivity such as Pt, Ag, or Cu. Further, the conductor layer 2 shows a higher reflectance than the information recording medium 7.

  The conductor layer 2 has, for example, two electrode portions 21 that are rectangular, for example, arranged in the track direction. These electrode portions 21 have convex portions that protrude in two steps, for example, in two opposing directions and become narrower in steps. This convex portion is composed of a first convex portion 22 and a second convex portion 23, and the tip portions of the second convex portion 23 are connected by the narrowed portion 12.

  Wiring for applying a current to the conductor layer 2 is performed using the electrode portion 21. However, since the conductor layer 2 faces the information recording medium 7, an electrode is formed on the side surface of the recording head 3 so as to be electrically connected to the electrode 21, and wiring is performed on this electrode. If the area of the conductor layer 2 is small, the conductor layer 2 may be damaged by heat when a current is passed through the conductor layer 2. For this reason, the durability of the conductor layer 2 is improved by increasing the area of the electrode portion 21 and forming a convex portion whose width gradually decreases.

  FIG. 4B is an enlarged schematic view of the vicinity of the narrowed portion 12 in the conductor layer 2. For example, as shown in the figure, the constricted portion 12 has a semicircular arc shape, and is formed using, for example, photolithography. In this embodiment, the distance X1 between the first protrusions 22 is 20 μm, the distance X2 between the second protrusions 23 is 0.5 μm, the width Y1 of the first protrusions 22 is 30 μm, and the second protrusions 23. Width Y2 = 5 μm, outer diameter Y3 of constriction 12 = 0.5 μm, and width Y4 of arcuate portion of constriction 12 = 0.25 μm.

  In the constricted portion 12, when a current flows, a magnetic field perpendicular to the information recording medium 7 (in FIG. 4, from the front side to the back side or from the back side to the front side) is generated according to the right-screw rule. By this magnetic field and the leaked light 10 from the constricted portion 12, perpendicular recording can be performed on a magnetic layer made of, for example, TbFeCo formed on the information recording medium 7.

  In this embodiment, X2 = 0.5 μm as described above. As a result, the width of the leaked light 10 from the narrowed portion 12 to the information recording medium 7 is 0.5 μm at the maximum. However, it is possible to generate near-field light by a combination of the metal forming the conductor layer 2 and the wavelength of the light source 4, whereby the width of the leakage light 10 can be made very narrow. Further, the width of the leaked light 10 can be further controlled by the power of the irradiated light and the thermal sensitivity of the information recording medium 7. The thermal sensitivity of the information recording medium 7 can be adjusted by the thickness of the magnetic layer and the dielectric layer, or the presence or absence of a metal layer.

  Note that a control system such as focusing for recording / reproducing, a signal processing system, and a spindle control system for rotating the information recording medium 7 are well known in the art. Omitted.

  Next, a method of controlling the position of the light from the light source 4 and the conductor layer 2 (constriction portion 12) will be described with reference to FIGS. In addition, since the irradiation position of light can be controlled by the detection signal obtained from the reflected light as described above, the detection signal will be described as a position error signal in the future. In the recording / reproducing apparatus of the present embodiment, the objective lens 5 is swung in the vertical direction to irradiate the conductor layer 2 or the information recording medium 7 with light. The distance between the recording head 3 and the information recording medium 7 was 10 nm. The reflected light at that time is detected by the position controller 8 as a position error signal, and the head driver 9 controls the position based on this position error signal. The position error signal is detected by the two-divided photodiode 14. The position error signal is the same signal as the focus error signal and is detected by, for example, the knife edge method.

  FIG. 5 shows a schematic view when the objective lens 5 is swung in the vertical direction by a drive unit (not shown) in the optical head 6 to irradiate the conductor layer 2 or the information recording medium 7 with light. The disc is rotating in the direction. In FIG. 5, reference numeral 13 denotes a beam spot of irradiated light. FIG. 5A is a schematic diagram illustrating a state in which light is applied to the conductor layer 2, and FIG. 5B is a schematic diagram illustrating a state in which the information recording medium 7 is irradiated with light through the substrate 1. is there. 5C and 5D are schematic views when the optical head 6 is viewed from the information recording medium 7 side, and FIG. 5C is a schematic view of the state shown in FIG. FIG. 5D shows a schematic diagram of the state shown in FIG.

  Here, as shown in FIGS. 5A and 5C, when the conductor layer 2 is irradiated with light, the conductor layer 2 has a higher reflectance than the information recording medium 7. As a result, a position error signal having a larger signal amplitude than that obtained when the beam 7 is irradiated can be obtained. On the other hand, as shown in FIGS. 5B and 5D, when the information recording medium 7 is irradiated with light, the information recording medium 7 has a reflectance higher than that of the conductor layer 2. Since it is low, a position error signal having a smaller signal amplitude than when the conductor layer 2 is irradiated can be obtained.

  FIG. 6 shows a position error signal obtained at this time. In FIG. 6, the horizontal axis represents time, and the vertical axis represents the signal level. FIG. 6A shows a position error signal obtained when the conductor layer 2 is irradiated with light as shown in FIGS. 5A and 5C. On the other hand, FIG. 6B shows a position error signal obtained when the information recording medium 7 is irradiated with light through the substrate 1 as shown in FIGS. 5B and 5D. Yes.

  Here, since the distance between the conductor layer 2 and the information recording medium 7 is 10 nm, both the conductor layer 2 and the information recording medium 7 are within the depth of focus. Therefore, since the focus point is suitable for both the conductor layer 2 and the information recording medium 7, a position error signal having the same shape can be obtained. However, the signal amplitude from the conductor layer 2 becomes larger due to the difference in reflectance between the two. Therefore, it is possible to determine the light irradiation position from the magnitude of the obtained signal amplitude. Further, after determining whether the light is on the conductor layer 2 or on the information recording medium 7 from the obtained signal amplitude, the recording head 3 is moved by the head driving unit 9 to irradiate the recording head 3 with light. Move position. At this time, since the shape of the conductor layer 2 is known in advance, the light can be controlled to move to a predetermined position (constriction portion 12).

  Further, when the beam spot 13 comes to the boundary between the conductor layer 2 and the information recording medium 7, position error signals having different signal amplitudes are obtained. This will be described with reference to FIG.

  FIG. 7 is a schematic diagram when the beam spot 13 is located at the boundary between the conductor layer 2 and the information recording medium 7 parallel to the X-axis direction such as 15 and 19. FIG. 7A shows the position (15, 19) of the beam spot 13 and the two-divided photodiode 14. In the two-divided photodiode 14, the light receiving portion is divided into a first light receiving portion 14 a and a second light receiving portion 14 b (on the paper surface, upper part and lower part) by a dividing line in the X-axis direction. FIG. 7B is a diagram showing the principle of detection of the position error signal, and shows a state where the beam spot 13 is located at the boundary of the irradiated object having different reflectivities. In FIG. 7B, for the sake of simplicity, the state in which the irradiated object 16 moves away from or approaches the objective lens 17 is taken as an example. That is, although the objective lens 17 is actually oscillating with respect to the irradiated pair 16, in principle, it is the same as the operation shown in FIG. FIGS. 7C and 7D show the detected position error signals.

  First, consider the case where the beam spot 13 is at the position 15. In FIG. 7A, reference numeral 14 denotes a two-divided photodiode. In FIG. 7B, reference numeral 16 denotes an irradiated body having a different reflectance. A hatched portion indicates an irradiated body having a high reflectance (corresponding to the conductor layer 2), and a non-hatched portion has a low reflectance. An irradiated body (corresponding to the information recording medium 7) is shown. Reference numeral 17 denotes an objective lens, and 18 denotes a knife edge.

  7B, the state (A) is a state in which the beam spot 13 is approaching the objective lens 17 from the in-focus position, and the state (B) is a state in which the beam spot 13 is in focus. (C) represents a state in which the beam spot 13 is away from the in-focus position with respect to the objective lens 17. In FIG. 7B, the solid line represents the reflected light from the irradiated body in the state (B), the dotted line represents the reflected light from the irradiated body in the state (C), and the one-dot oblique line represents the state (A). Each of the reflected light from the irradiated object is shown. In the two-divided photodiode 14 shown in FIG. 7A, the beam spot 13 in the state (B) is arranged at the focal position at the time of focusing.

  Here, in the state (A) where the beam spot 13 is approaching from the in-focus position, the reflected light from the irradiated object (information recording medium 7 side) having a low reflectance is reflected into the two-part photo. It is detected by one first light receiving portion 14a of the diode 14. On the other hand, the reflected light from the irradiated object (on the conductor layer 2 side) having a high reflectance is blocked by the knife edge. On the contrary, in the state (C) where the beam spot 13 is away from the in-focus position, the reflected light from the irradiated object (information recording medium 7 side) having a low reflectance is blocked by the knife edge. On the other hand, the reflected light from the irradiated object (conductor layer 2) having a high reflectance is detected by the second light receiving portion 14b of the two-divided photodiode 14.

  The position error signal is obtained by taking the differential of each light receiving part of the two-divided photodiode 14. In this case, in the state (A), the detection signal from the first light receiving unit 14a becomes a position error signal, and in the state (C), the detection signal from the second light receiving unit 14b becomes a position error signal. For this reason, when the signal amplitude obtained in the state (A) is compared with the signal amplitude obtained in the state (C), the signal amplitude obtained in the state (A) becomes smaller due to the difference in reflectance. In the state (B), since the two-divided photodiode 14 is disposed at the focal position, the signal amplitude is zero. When such a phenomenon is considered continuously, a position error signal as shown in FIG. 7C is obtained. Similarly, when the beam is at position 19, a position error signal as shown in FIG. 7D is obtained.

  However, the positional relationship between the first light receiving unit 14a and the second light receiving unit 14b (the vertical relationship in FIG. 7A) and the amplitude relationship may be reversed depending on the light receiving method and signal processing. . As described above, if the boundary between the conductor layer 2 and the information recording medium 7 is detected, the positional relationship between the beam spot 13 and the narrowed portion 12 can be controlled more precisely.

  As described above, in the present recording / reproducing apparatus, the positional relationship between the irradiation position of the light from the light source 4 and the narrowed portion 12 can be controlled. Therefore, in order to confirm this function, an experiment was conducted in which the beam spot 13 was moved to the position of the constricted portion 12. The results will be described in the following examples with reference to FIG. 1, FIG. 8, and FIG.

Example 1
First, a recording / reproducing apparatus as shown in FIG. 1 was produced. At this time, the conductor layer 2 made of Au was formed on the recording head 3. The conductor layer 2 has a reflectance of 95% and has a shape as described above. A semiconductor laser having a wavelength of 630 nm is used as the light source 4 and the objective lens 5 has NA = 0.65. At this time, the spot diameter of the light is about 1 μm. Therefore, the beam spot diameter is larger than the width X2 (shape) of the narrowed portion 12 of 0.5 μm.

  The position control unit 8 controls the position of the recording head 3 based on the position error signal detected by the two-divided photodiode 14 from the reflected light of the conductor layer 2 or the information recording medium 7. As described above, the two-divided photodiode 14 is arranged so that the boundary portion between the second convex portion 23 of the conductor layer 2 parallel to the X-axis direction and the information recording medium 7 can be detected. The position control unit 8 was made to recognize the shape of the conductor layer 2 described above in advance. The head drive unit 9 is composed of a piezoelectric element, has a movable range of ± 50 μm, and a practical positioning accuracy of 10 nm. In this embodiment, the information recording medium 7 was rotated at 1200 per minute (rpm) in the direction from + to − on the Y axis shown in FIG. However, the direction of rotation is not limited to this.

  First, when a laser beam was emitted from the light source 4 and applied to the recording head 3, (1) a position error signal having the same amplitude was detected both above and below the signal waveform. As a result, it has been found that the beam spot 13 is highly likely to be irradiated on the conductor layer 2 or the information recording medium 7. Next, from this state, the recording head 3 was moved in the X-axis direction by the head driving unit 9. As a result, due to the movement in the − (minus) direction, the position error signal (2) once decreased in signal amplitude, and (3) continued to decrease, and the signal amplitude became approximately half. When the position error signal was further moved in the same direction (− direction), the position error signal was (4) temporarily increased in signal amplitude and (5) continuously recovered to the original signal amplitude.

  To explain this phenomenon, the signal amplitude decreased because the position of the beam spot 13 moved from the conductor layer 2 to the information recording medium 7. That is, the reflectance of the conductor layer 2 is 95% as described above, and the reflectance of the information recording medium 7 is 45%. Therefore, the signal amplitude is halved by the above movement. The signal amplitude once decreased because the beam spot 13 just reached the boundary between the conductor layer 2 and the information recording medium 7. Since this boundary is not parallel to the X direction but parallel to the Y direction, the position error signal does not produce a difference between the upper amplitude and the lower amplitude, and the signal amplitude simply decreases.

  Next, the beam spot 13 was returned to the point where the signal amplitude was reduced by half, and the beam spot 13 was moved in the Y direction. As a result, due to the movement in the-direction, (6) the upper part of the signal amplitude once became about twice as large as the lower part, and then the lower part of the signal amplitude became about twice as constant. Thereafter, (7) the lower part of the signal amplitude increased and the upper part returned to the original amplitude.

  To explain this phenomenon, the signal amplitude increased because the position of the beam spot 13 moved from the information recording medium 7 to the conductor layer 2. At this time, the reason why the upper portion of the signal amplitude is about twice as large as that of the lower portion is that the boundary in the X direction between the conductor layer 2 and the information recording medium 7 is detected. Thereafter, the lower amplitude also increased as the beam spot 13 moved onto the conductor layer 2. When the beam spot 13 further moved, passed through the second convex portion 23, and again reached the information recording medium 7, the upper amplitude first returned to the original amplitude.

The relationship between the movement of the series of beam spots 13 and the position error signal is shown in FIGS.
At the time of the above-mentioned (1), the beam spot 13 is considered to be at the position of FIG. 8A, and the position error signal at that time is as shown in FIG. 9A.

  When the signal amplitude is once reduced in (2), the beam spot 13 is on the boundary between the conductor layer 2 and the information recording medium 7 as shown in FIG. 8B, and the position error signal at that time is shown in FIG. It became like b).

  In the state (3), the beam spot 13 is on the information recording medium 7 as shown in FIG. In this case, since the reflectance of the information recording medium 7 is about 50% lower than that of the conductor layer 2, the signal amplitude is halved from the state of FIG. 9A to the state of FIG. 9C.

  The state in which the signal amplitude once increased in (4) occurred because the beam spot 13 again reached the boundary between the conductor layer 2 and the information recording medium 7 from above the information recording medium 7 as shown in FIG. . In this case, the signal amplitude increased as shown in FIG.

  Further, the reason why the upper part of the signal amplitude in (6) is about twice as large as the lower part is that the beam spot 13 has moved from the information recording medium 7 to the conductor layer 2 as shown in FIG. Thus, in the recording / reproducing apparatus, the difference in reflectance between the conductor layer 2 and the information recording medium 7 can be accurately determined by the two-divided photodiode 14 and detected as a difference in signal amplitude. As a result, the signal shown in FIG. 9 (e) was detected. Thereafter, the beam spot 13 further moved on the conductor layer 2, so that the lower amplitude was the same as the upper amplitude.

  The reason that the lower part of the signal amplitude in (7) is increased and the upper part returns to the original amplitude is that the beam spot 13 is further moved in the Y direction, and again as shown in FIG. This is because it reached the boundary between the conductor layer 2 and the information recording medium 7. As a result, as shown in FIG. 9 (f), the lower part is about twice as large as the upper part, contrary to the signal amplitude difference of (6). Also here, the difference in reflectance between the conductor layer 2 and the information recording medium 7 can be accurately determined by the two-divided photodiode 14, and can be detected as a difference in signal amplitude.

  Further, when the amount of movement (X1) of the beam spot 13 from (2) to (4) and the amount of movement (Y2) of the beam spot 13 from (6) to (7) were measured, 20.25 μm, It was 4.98 μm. As described above, since the conductor layer 2 is produced with the sizes of X1 = 20 μm and Y2 = 5 μm, it can be seen that the irradiation position of the beam spot 13 can be accurately controlled even in the movement amount.

  As described above, in the present recording / reproducing apparatus, it has been found that the position of the beam spot 13 can be accurately grasped according to the shape of the conductor layer 2, so that the beam spot 13 is continuously moved to the narrowed portion 12. saw.

  After moving from the state (7) (FIG. 8 (f), FIG. 9 (f)) to the state (6) again (FIG. 8 (e), FIG. 9 (e)), the + direction of X continues. The recording head 3 was moved. As a result, at the start of movement, as shown in FIG. 9E, a position error signal with a large amount of reflected light from the conductor layer 2 was detected, but when moved 5 μm, the position shown in FIG. An error signal was detected. This is presumably because the beam spot 13 is located at the position shown in FIG. That is, the lower part of the beam spot 13 on the drawing is detected as reflected light from the information recording medium 7, and the upper part is detected as reflected light from the information recording medium 7 and a part of the conductor layer 2. For this reason, a position error signal in which the upper amplitude is larger than the lower amplitude is detected. The lower amplitude coincided with the position error signal amplitude in FIG. 8C (FIG. 9C).

  Subsequently, when the recording head 3 was moved 5 μm in the negative Y direction, a position error signal shown in FIG. 9H was detected. As shown in FIG. 8 (h), this is because both the upper and lower portions of the beam spot 13 are irradiated to a part of the information recording medium 7 and the conductor layer 2, and the reflected light therefrom is detected. It is done. When the recording head 3 is further moved in the negative Y direction, the upper amplitude gradually decreases and the lower amplitude also decreases, and becomes constant with the same position error signal as in FIG. 9C. This is because the beam spot 13 has passed through the narrowed portion 12 and moved again onto the information recording medium 7.

  In the recording / reproducing apparatus of the present embodiment, the position of the beam spot 13 can be controlled by the method described above. Next, the beam spot 13 was moved to the narrowed portion 12 and recording was actually performed. In this example, the distance between the semiconductor laser having a wavelength of 630 nm, the conductor layer 2 formed of Au, and the recording head 3 and the information recording medium 7 was set to 10 nm, and near-field recording was performed.

  When a recording magnetic field having a frequency of 3.14 MHz is applied to the conductor layer 2 (constriction portion 12) at a radius of 25 mm and light of 5 mW is irradiated from the light source 4, a recording mark with ML = 0.5 μm can be recorded. did it. As a result, it has been found that the positions of the beam spot 13 and the constriction 12 can be accurately controlled.

  As described above, according to the present recording / reproducing apparatus, the positional relationship between the beam spot 13 and the narrowed portion 12 is determined by comparing the position error signal from the conductor layer 2 with the position error signal from the information recording medium 7. It can be controlled accurately.

  If, for example, an increase / decrease in signal amplitude is detected with reference to a position error signal at the time when the beam spot 13 and the constricted portion 12 coincide with each other and feedback is performed by the head drive unit 9, the coincidence between the beam spot 13 and the constricted portion 12 occurs. It is also possible to maintain the positional relationship.

  In the above description, the beam spot 13 is initially present on the conductor layer 2 as an example. However, even when the beam spot 13 initially exists on the information recording medium 7 or on the boundary between the conductor layer 2 and the information recording medium 7 and the position error signal is detected, the beam spot 13 is similarly based on the position error signal. Position control of the beam spot 13 and the constriction part 12 can be performed.

[Embodiment 2]
Another embodiment according to the recording / reproducing apparatus of the present invention will be described. In the first embodiment, the case where the position error signal can be detected from both the conductor layer 2 and the information recording medium 7 has been described. On the other hand, the present embodiment accurately controls the positional relationship between the beam spot 13 and the constricted portion 12 when position information cannot be simultaneously detected from both the conductor layer 2 and the information recording medium 7. For example, unlike the first embodiment, this is the case where the position of the objective lens exceeds the dynamic range of position error signal detection in the position controller 8. In the present embodiment, the conductor layer 2 is formed of Cu. In this case, the reflectance of the conductor layer 2 is 95%. Other than that, the same recording / reproducing apparatus as in the first embodiment and the photodiode 14 are used.

  In the recording / reproducing apparatus of the present embodiment, first, the suspension to which the recording head 3 is attached is adjusted so that the flying height of the recording head 3 from the information recording medium 7 is 2 μm. In the optical system of the present recording / reproducing apparatus, it is impossible to simultaneously detect the position error signal from the conductor layer 2 and the information recording medium 7.

  Next, the recording head 3 was irradiated with laser light, and a position error signal was detected while changing the height of the optical head 6 and the position of the recording head 3 (X direction and Y direction in FIG. 8). As a result, a position error signal having a large signal amplitude and a position error signal having a small signal amplitude were detected. These are a position error signal from the conductor layer 2 having a high reflectance and a position error signal from the information recording medium 7 having a low reflectance.

  Here, a better position error signal can be detected with a larger signal amplitude. Accordingly, in the present embodiment, (1) the height of the optical head 6 and the position of the recording head 3 (X direction and Y direction in FIG. 8) are set so that the beam spot 13 can be initially irradiated onto the conductor layer 2. It was adjusted.

  Next, the recording head 3 was moved in the X-axis direction by the head driving unit 9. In this case, due to the movement in the-direction, (2) the signal amplitude of the position error signal once decreased, and (3) thereafter, the signal amplitude could not be detected at all. Thereafter, when the recording head 3 was further moved in the same direction (− direction), (4) the signal amplitude once increased, and (5) a phenomenon that the original signal amplitude was continuously recovered was observed.

  Explaining this phenomenon, the signal amplitude cannot be detected in (3) because the position of the beam spot 13 has moved from the conductor layer 2 to the information recording medium 7. As described above, since the height of the optical head 6 is adjusted so that the position error signal from the conductor layer 2 can be detected, the position error signal is not detected from the information recording medium 7.

  The reason that the signal amplitude once decreased in (2) is that the beam spot 13 has just reached the boundary between the conductor layer 2 and the information recording medium 7. That is, since the position error signal can be detected only from the portion of the beam spot 13 irradiated on the conductor layer 2, the amplitude is reduced.

  Next, the beam spot 13 was returned to a point where the signal amplitude was not detected, and the beam spot 13 was moved in the Y direction. As a result, due to the movement in the-direction, (6) only the upper part of the signal amplitude was once detected, and subsequently the lower signal was detected, and the upper and lower parts had the same amplitude. After that, (7) from a constant signal amplitude, detection was made only from the bottom, and no signal was detected.

  Describing this phenomenon, the signal was detected only from the upper part because the position of the beam spot 13 moved from the information recording medium 7 to the conductor layer 2. At this time, only the upper portion of the signal amplitude was detected because the boundary in the X direction between the conductor layer 2 and the information recording medium 7 was detected. Thereafter, as the beam spot 13 moves on the conductor layer 2, the lower amplitude also increases, and further moves to approach the information recording medium 7 again, so that only the lower amplitude is detected this time. Further, when the beam spot position moves on the information recording medium 7, no position error signal is detected.

The relationship between the movement of the series of beam spots 13 and the obtained position error signal is shown in FIGS.
At the time of (1) described above, the beam spot 13 is considered to be at the position shown in FIG. 8A, and the position error signal at that time is as shown in FIG.

  When the signal amplitude is once reduced in (2), the beam spot 13 is on the boundary between the conductor layer 2 and the information recording medium 7 as shown in FIG. 8B, and the position error signal at that time is shown in FIG. It became like b).

  In the state (3), the beam spot 13 is on the information recording medium 7 as shown in FIG. In this case, the position error signal cannot be detected. That is, the position error signal changes from the state of FIG. 10B to the state of FIG. 10C, and the signal cannot be obtained.

  The state in which the signal amplitude once increased in (4) occurred because the beam spot 13 again reached the boundary between the conductor layer 2 and the information recording medium 7 from above the information recording medium 7 as shown in FIG. . In this case, the signal amplitude increased as shown in FIG.

  In the state of (5), since the beam spot 13 comes again on the conductor layer 2, the same signal amplitude as in FIG. 10A was obtained.

  The reason why only the upper part of the signal amplitude is detected in (6) is that the beam spot 13 has moved from the information recording medium 7 to the conductor layer 2 as shown in FIG. Thus, in the recording / reproducing apparatus, the difference between the conductor layer 2 and the information recording medium 7 can be accurately determined by the two-divided photodiode 14, and the position error signal from the conductor layer 2 can be detected. As a result, the signal shown in FIG. 9 (e) was detected. Thereafter, the beam spot 13 further moved on the conductor layer 2, so that the lower amplitude was the same as the upper amplitude.

  Thereafter, detection was performed only from the lower part from the constant signal amplitude of (7). This is because the boundary between the conductor layer 2 and the information recording medium 7 is reached again as shown in FIG. As a result, as shown in FIG. 10 (f), only the lower amplitude was detected, contrary to (6). Also here, the conductor layer 2 and the information recording medium 7 can be accurately discriminated by the two-divided photodiode 14, and the position error signal from the conductor layer 2 can be detected. Furthermore, since the beam spot 13 has moved in the Y direction and has again moved onto the information recording medium 7, no position error signal can be detected.

  Further, when the movement amount (X1) of the beam spot 13 from (2) to (4) and the movement amount (Y2) of the beam spot 13 from (6) to (7) were measured, they were 20.34 μm, It was 5.09 μm. As described above, since the conductor layer 2 is produced with the sizes of X1 = 20 μm and Y2 = 5 μm, it can be seen that the irradiation position of the beam spot 13 can be accurately controlled even in the movement amount.

  Thus, in this recording / reproducing apparatus, it was found that the position of the beam spot 13 could be accurately grasped according to the shape of the conductor layer 2, and the beam spot 13 was subsequently moved to the constricted portion 12. .

  After moving from the state (7) (FIG. 8 (f), FIG. 10 (f)) to the state (6) again (FIG. 8 (e), FIG. 10 (e)), the negative X direction is continued. The recording head 3 was moved. As a result, at the start of movement, as shown in FIG. 10 (e), the position error signal only from the conductor layer 2 was detected, but when the movement was 5 μm, the position error signal as shown in FIG. 10 (g) was detected. did. This is presumably because the beam spot 13 is located at the position shown in FIG. That is, since the lower part of the beam spot 13 in the drawing is on the information recording medium 7, the position error signal cannot be detected by this reflected light. Further, since the upper part of the beam spot 13 on the drawing is on a part of the information recording medium 7 and the conductor layer 2, it is detected as reflected light from the conductor layer 2. For this reason, a position error signal having an amplitude smaller than that in the state (6) was detected.

  Subsequently, when the beam spot 13 was moved in the + direction of Y by 5 μm, the position error signal shown in FIG. 10 (h) was detected. This is considered to be because both the upper and lower portions of the beam spot 13 are irradiated to a part of the information recording medium 7 and the conductor layer 2 as shown in FIG. Furthermore, since the amount of light reflected from the conductor layer 2 is larger in the upper part than in the lower part (since the proportion of the conductor layer 2 is larger), it is considered that the upper amplitude is larger than the lower amplitude. Thereafter, when the beam spot 13 is further moved in the + direction of Y, the position error signal cannot be detected as in FIG. This is because the beam spot 13 has passed through the narrowed portion 12 and moved again onto the information recording medium 7.

  In the recording / reproducing apparatus of the present embodiment, the position of the beam spot 13 can be controlled by the method described above. Next, the beam spot 13 was moved to the narrowed portion 12 and recording was actually performed. As in Example 1, when a recording magnetic field with a frequency of 3.14 MHz was applied to the conductor layer 2 (constriction 12) at a radius of 25 mm and light of 5 mW was irradiated from the light source 4, the recording magnetic field and constriction 12 The recording mark of ML = 0.5 μm could be recorded by the leaked light. As a result, it has been found that the positions of the beam spot 13 and the constriction 12 can be accurately controlled. Further, in the present embodiment, since the conductor layer 2 is formed of Cu and the flying height is 2 μm, it is considered that the recording was performed not by the near-field light but by the normal leakage light.

[Embodiment 3]
Another embodiment according to the recording / reproducing apparatus of the present invention will be described. In the recording / reproducing apparatus of the present embodiment, the irradiation position of light is controlled using a four-division photodiode instead of the two-division photodiode 14. The configuration will be described with reference to FIG.

  Note that the detection principle of the position error signal is the same as that when the two-divided photodiode 14 is used, and the description is omitted here because it has been described with reference to FIG. 7B in the first embodiment. . Further, other configurations such as the conductor layer 2 and the information recording medium 7 are the same as those in the first and second embodiments. In FIG. 11, the same reference numerals are used to indicate the same parts as those in FIG.

  FIG. 11A shows a case where the beam spot 13 exists at the boundary between the conductor layer 2 parallel to the X-axis direction and the information recording medium 7 as in 15 and 19 shown in FIG. FIG. 10 is a schematic diagram illustrating a case in which the information recording medium 7 exists at the boundary between the conductor layer 2 and the information recording medium 7 parallel to the Y-axis direction as in 101 and 102.

  In the figure, reference numeral 100 denotes a four-divided photodiode. The four-divided photodiode 100 includes a first light-receiving unit 100a (on the right side of the paper, upper right), a second light-receiving unit, and a second line. The light receiving unit 100b is divided into a third light receiving unit 100c (on the paper, the lower left side) and a fourth light receiving unit 100d (the upper left side on the paper). The position error signal can be detected by calculating a signal detected by each light receiving unit.

  For example, the signal received by the first light receiving unit 100a and the signal received by the fourth light receiving unit 100d are added together and regarded as one detection signal (100a + 100d), and the signal received by the second light receiving unit 100b and the third light receiving unit The signal received at 100c is added and regarded as one detection signal (100b + 100c). As a result, the four-divided photodiode 100 has the same function as the two-divided photodiode 14 divided in the Y-axis direction by the dividing line parallel to the X-axis as shown in the first embodiment. That is, the position error signal can be detected by taking a differential of (100a + 100d) − (100b + 100c). Therefore, as in the first embodiment, when the beam spot 13 exists at the position 15, a position error signal as shown in FIG. 11B is obtained, and when the beam spot 13 exists at the position 19, a position error signal as shown in FIG. it can. When the beam spot 13 exists at the position 101 or 102, a position error signal as shown in FIG. Here, the detection method of the position error signal is assumed to be X type.

  Next, the signal received by the first light receiving unit 100a and the signal received by the second light receiving unit 100b are added to be regarded as one detection signal (100a + 100b), and the signal received by the third light receiving unit 100c and the fourth light receiving are received. The signal received by the unit 100d is added and regarded as one detection signal (100c + 100d). As a result, the four-divided photodiode 100 has the same function as the two-divided photodiode divided in the X-axis direction by a dividing line parallel to the Y-axis. That is, the position error signal can be detected by taking a differential of (100a + 100b) − (100c + 100d). Therefore, in this case, a position error signal as shown in FIG. 11B can be obtained when the beam spot 13 exists at the position 101, and a position error signal as shown in FIG. On the other hand, when the beam spot 13 exists at the position 15 or 19, a position error signal as shown in FIG. Such a position error signal detection method is assumed to be Y type here.

  As described above, when the four-divided photodiode 100 is used, by calculating signals obtained from the four light receiving units, the two-divided photodiode divided in the X-axis direction and the two divided in the Y-axis direction are calculated. It can also function as a split photodiode. Thereby, the position control in the X-axis direction and the position control in the Y-axis direction can be performed precisely. The magnitude relationship between the amplitudes may be reversed depending on how light is received and signal processing.

  As described above, also in this embodiment, the positional relationship between the irradiation position of light from the light source 4 and the constricted portion 12 can be controlled. Therefore, in order to confirm this function, an experiment was conducted in which the beam spot 13 was moved to the position of the constricted portion 12. Since this experiment was performed in the same manner as in the first embodiment, in the following examples, FIG. 8 is used for the movement of the beam spot 13, and FIGS. 12 and 13 are used for the obtained position error signal. Each will be explained. FIG. 12 shows a position error signal for the X type, and FIG. 13 shows a position error signal for the Y type. The experimental conditions are the same as in Example 1 of the first embodiment as described above, and are omitted here.

Example 1
A laser beam was emitted from the light source 4 and (1) when it was irradiated onto the conductor layer 2 of the recording head 3, the X type detected a position error signal having the same amplitude both above and below the signal waveform. In the Y type as well, a position error signal having the same amplitude was detected both above and below the signal waveform. This is because all of the four-divided light receiving surfaces of the four-divided photodiode 100 detect the reflected light from the conductor layer 2, and the same result can be obtained in both the X-type calculation and the Y-type calculation. is there.

  The relationship between the movement of the series of beam spots 13 and the position error signal is shown in FIG. 8, FIG. 12, and FIG.

  In the case of the above-mentioned (1), the beam spot 13 is considered to be at the position of FIG. 8A, and all the four-divided light receiving surfaces detect reflected light from the conductor layer 2. The position error signal is as shown in FIG. 12A for the X type and as shown in FIG. 13A for the Y type, and the same position error signal was obtained.

  Next, from this state, the recording head 3 was moved in the X-axis direction by the head driving unit 9. As a result, due to the movement in the − (minus) direction, in the X type, the position error signal (2) once decreased in signal amplitude, and (3) continued to decrease, and the signal amplitude became approximately half. When the position error signal was further moved in the same direction (− direction), the position error signal was (4) temporarily increased in signal amplitude and (5) continuously recovered to the original signal amplitude.

  To explain this phenomenon, the signal amplitude decreased because the beam spot 13 moved from the conductor layer 2 to the information recording medium 7. That is, this is due to the difference between the reflectance of the conductor layer 2 (95%) and the reflectance of the information recording medium 7 (45%). The signal amplitude once decreased because the beam spot 13 just reached the boundary between the conductor layer 2 and the information recording medium 7. In this case, since the boundary between the conductor layer 2 and the information recording medium 7 is parallel to the Y direction instead of the X direction, there is no difference between the upper amplitude and the lower amplitude in the X type position error signal. Instead, the signal amplitude simply decreased.

  In the movement of the beam spot from (2) to (5), in the Y type error signal, (2) the upper part of the signal amplitude once decreases to about half of the lower part, and (3) the signal amplitude of the lower part continues. After reducing to about half of the case of (1), (4) the upper part of the signal amplitude once becomes about twice as large as the lower part, and (5) the lower part of the signal amplitude is about twice as long as the original signal amplitude. It recovered to a constant level.

  To explain this phenomenon, the signal amplitude decreased as shown in (3) because the position of the beam spot 13 moved from the conductor layer 2 to the information recording medium 7. That is, this is due to the difference between the reflectance of the conductor layer 2 (95%) and the reflectance of the information recording medium 7 (45%). The reason why the upper part of the signal amplitude once decreased to about half of the lower part as in (2) is that the beam spot 13 has just reached the boundary between the conductor layer 2 and the information recording medium 7. That is, the Y type has a light receiving surface that is divided into the left and right sides (X-axis direction) on the paper surface. Therefore, either one of the light receiving surfaces detects the reflected light from the conductor layer 2 and the other side. Reflected light from the information recording medium layer 7 is detected on the light receiving surface. As a result, the reflectance of the information recording medium layer 7 is about half of the reflectance of the conductor layer 2, and this difference in reflectance is detected as an amplitude difference. This indicates that the detection signals detected on each light receiving surface can be accurately calculated. In (4), since the beam spot 13 again reaches the boundary between the conductor layer 2 and the information recording medium 7, the upper portion of the signal amplitude once becomes about twice as large as the lower portion. At this time, since the detection positions of the conductor layer 2 and the information recording medium 7 are opposite to those in the case of (2), the signal amplitude is recovered from the upper part of the amplitude, and subsequently the original amplitude amount is obtained in (5). became.

  The relationship between the movement of the series of beam spots 13 and the position error signal is shown in FIG. 8, FIG. 12, and FIG.

  When the signal amplitude is once reduced in the X type (2), the beam spot 13 is on the boundary between the conductor layer 2 and the information recording medium 7 as shown in FIG. FIG. 12B shows the X type. At this time, the Y type is as shown in FIG. This is because the Y type detects the boundary between the conductor layer 2 and the information recording medium 7 in the Y direction because the calculation is performed like a photodiode divided in the X-axis direction.

  In the state (3), the beam spot 13 is on the information recording medium 7 as shown in FIG. In this case, since the reflectance of the information recording medium 7 is about 50% lower than that of the conductor layer 2, in the X type, the signal amplitude is halved from the state of FIG. 12 (a) to the state of FIG. 12 (c). In the Y type as well, the signal amplitude is halved from the state of FIG. 13A to the state of FIG.

  The state where the signal amplitude once increased in the X type of (4) is because the beam spot 13 again reaches the boundary between the conductor layer 2 and the information recording medium 7 from above the information recording medium 7 as shown in FIG. Occurred. In this case, in the X type, the signal amplitude increased as shown in FIG. 12 (d), and in the Y type, the upper signal amplitude recovered as shown in FIG. 13 (d). This is because the boundary between the Y-direction conductor layer 2 and the information recording medium 7 is detected again.

  In the state of (5), the beam spot 13 is present on the conductor layer 2 as in (1). Therefore, the position error signal is shown in FIG. 12 (a) for the X type and FIG. 13 (a) for the Y type. A similar position error signal was obtained.

  Next, the beam spot 13 was returned to the point where the signal amplitude was reduced by half, and the beam spot 13 was moved in the Y direction. As a result, due to the movement in the − direction, in the X type, (6) the upper part of the signal amplitude once became about twice as large as the lower part, and then the lower part of the signal amplitude became about twice as constant. Thereafter, (7) the lower part of the signal amplitude increased and the upper part returned to the original amplitude.

  To explain this phenomenon, the signal amplitude increased because the position of the beam spot 13 moved from the information recording medium 7 to the conductor layer 2. At this time, the reason why the upper portion of the signal amplitude is about twice as large as that of the lower portion is that the boundary in the X direction between the conductor layer 2 and the information recording medium 7 is detected. In other words, the X type has a light receiving surface that is divided in the vertical direction (Y-axis direction) on the paper surface, and the reflected light from the conductor layer 2 is detected by one of the light receiving surfaces, and the other is detected. The reflected light from the information recording medium layer 7 is detected on the light receiving surface. As a result, since the reflectance of the information recording medium layer 7 is about half of the reflectance of the conductor layer 2, this difference in reflectance is detected as an amplitude difference. This indicates that the detection signals detected on each light receiving surface can be accurately calculated.

  Thereafter, the lower amplitude also increased as the beam spot 13 moved onto the conductor layer 2. When the beam spot 13 further moved, passed through the second convex portion 23, and again reached the information recording medium 7, the upper amplitude first returned to the original amplitude.

  In the movement of the beam spot from (6) to (7), in the Y type, (6) the signal amplitude increases, and when the beam spot 13 moves on the conductor layer 2 thereafter, the signal amplitude increases to about twice. (7) The amount of amplitude decreased again.

  Explaining this phenomenon, the signal amplitude increases when the position of the beam spot 13 is at the boundary in the X direction between the conductor layer 2 and the information recording medium 7. Since the recording medium layer 7 is about twice as large, the signal amplitude is also about twice as large. Thereafter, the beam spot 13 further moved and again reached the boundary in the X direction between the conductor layer 2 and the information recording medium 7, so that the amount of amplitude decreased.

  The relationship between the movement of the series of beam spots 13 and the position error signal is shown in FIG. 8, FIG. 12, and FIG.

  The reason why the upper part of the signal amplitude is twice larger than the lower part in the X type (6) is that the beam spot 13 has moved from the information recording medium 7 to the conductor layer 2 as shown in FIG. is there. As described above, since the calculation is performed in the X type like a photodiode divided in the Y-axis direction, a difference in reflectance between the conductor layer 2 and the information recording medium 7 is detected. For this reason, the boundary in the X direction can be accurately detected, so that it can be detected as a difference in signal amplitude. As a result, the signal shown in FIG. 12 (e) can be obtained. Thereafter, the beam spot 13 further moved on the conductor layer 2, so that the lower amplitude was the same as the upper amplitude. At this time, in the Y type, the signal amplitude decreased on the boundary between the conductor layer 2 and the information recording medium 7 as shown in FIG.

  In the X type of (7), the lower part of the signal amplitude increases and the upper part returns to the original amplitude. The beam spot 13 further moves in the Y direction, and as shown in FIG. This is because the beam spot 13 has reached the boundary between the conductor layer 2 and the information recording medium 7. As a result, as shown in FIG. 12 (f), the lower part is about twice as large as the upper part, contrary to the signal amplitude difference of (6). Here too, the difference in reflectance between the conductor layer 2 and the information recording medium 7 can be accurately determined by the two-divided photodiode 14 and detected as a difference in signal amplitude. At this time, in the Y type, a position error signal as shown in FIG. 13 (f) in which the signal amplitude was reduced was obtained as in (6).

  Here, the movement amount (X1) of the beam spot 13 from (2) to (4) and the movement amount (Y2) of the beam spot 13 from (6) to (7) were measured. In the measurement with the X type, they were 20.25 μm and 4.98 μm, respectively. In the Y type, they were 20.01 μm and 5.12 μm, respectively.

  As described above, since the conductor layer 2 is produced with the sizes of X1 = 20 μm and Y2 = 5 μm, it can be seen that the irradiation position of the beam spot 13 can be accurately controlled even in the movement amount. In particular, the X type has a measured value of 4.98 μm with respect to the size of Y2 = 5 μm, and can be measured with very high accuracy. This is because the light receiving surface divided in the Y-axis direction is provided, so that the movement amount can be measured very accurately with respect to the movement in the Y direction.

  That is, in the Y type, the boundary between the conductor layer 2 and the information recording medium 7 is detected by halving the signal amplitude. Therefore, in this method, the signal amplitude is halved as a criterion for determination. However, the amount of decrease in the signal amplitude is not constant due to noise caused by disturbances, and some error occurs. For this reason, judgment criteria tend to be ambiguous. On the other hand, in the X type, the reflected light from the conductor layer 2 and the reflected light from the information recording medium 7 are separately received at the boundary between the conductor layer 2 and the information recording medium 7. In particular, since the reflected light from the conductor layer 2 has a high reflectance, a large signal amplitude can be obtained. Therefore, since the signal amplitude from the conductor layer 2 was used as a reference, it is considered that the measurement was possible with high accuracy.

  In the Y type, it was possible to measure 20.01 μm with respect to the size of X1 = 20 μm. This is because, for the same reason as described above, the Y type can measure the movement amount very accurately with respect to the movement in the X direction.

  Thereby, in this embodiment, the movement amount in the Y direction can be accurately measured by using the X type calculation, and the movement amount in the X direction can be accurately measured by performing the Y type calculation. all right. In other words, in the present embodiment, since the position error signal by the X type and the position error signal by the Y type are always detected, either position error signal can be selectively used depending on the moving direction, and thus more accurately. The amount of movement can be measured.

  As described above, it was found that the position of the beam spot 13 could be accurately grasped according to the shape of the conductor layer 2, so that the beam spot 13 was moved to the narrowed portion 12 continuously.

  From the state (7) (FIGS. 8 (f), 12 (f), and 13 (f)) described above, the state (6) (FIGS. 8 (e), 12 (e), and 13 (e) is again performed. After moving to ()), the recording head 3 was moved in the X direction. As a result, at the start of movement, in the X type, as shown in FIG. 12 (e), a position error signal with a large amount of reflected light from the conductor layer 2 was detected. A position error signal is detected. This is presumably because the beam spot 13 exists at a position as shown in FIG. That is, the lower part of the beam spot 13 on the drawing is detected as reflected light from the information recording medium 7, and the upper part is detected as reflected light from the information recording medium 7 and a part of the conductor layer 2. For this reason, a position error signal in which the upper amplitude is larger than the lower amplitude is detected. The lower amplitude coincided with the position error signal amplitude in FIG. 8C (FIG. 12C).

  Here, when the Y-type position error signal was confirmed, the upper and lower amplitude amounts were the same as shown in FIG. This is because, in the case of the Y type, the same position error signal as that of the photodiode divided in two on the left and right (X-axis direction) on the paper surface is detected, so that when the beam spot 13 exists at the position of FIG. This is because reflected light from the information recording medium 7 and a part of the conductor layer 2 is detected from both the left and right light receiving portions.

  More specifically, the four-divided photodiode 100 has four-divided light receiving surfaces 100a to 100d as shown in FIG. In this configuration, both the light receiving surface 100a and the light receiving surface 100d detect reflected light from the information recording medium 7 and part of the conductor layer 2, and both the light receiving surface 100b and the light receiving surface 100c reflect light from the information recording medium 7. Is detected. In the Y type, since the position error signal calculated by (100a + 100b) − (100c + 100d) is detected, the amplitude amounts above and below the signal amplitude are the same. In other words, since the upper and lower amplitude amounts coincide with each other, it can be said that the beam spot 13 exists at the position of FIG.

  Subsequently, when the recording head 3 was moved 5 μm in the negative Y direction, the position error signal shown in FIG. As shown in FIG. 8 (h), this is because both the upper and lower portions of the beam spot 13 are irradiated to a part of the information recording medium 7 and the conductor layer 2, and the reflected light therefrom is detected. It is done. In the movement of the beam spot 13, in the Y type, as shown in FIG. 13 (h), a position error signal having the same vertical amplitude is detected. This is due to the reason as described above. In other words, in the position error signal detected by the Y type, if the upper and lower amplitude amounts are the same, the beam spot can move in parallel in the Y direction. It shows that.

  Further, when the recording head 3 is moved in the Y direction, the upper amplitude gradually decreases and the lower amplitude also decreases. The X type is the same as FIG. 12C, and the Y type is FIG. 13C. It became constant with the same position error signal. This is because the beam spot 13 has passed through the narrowed portion 12 and moved again onto the information recording medium 7.

  In the recording / reproducing apparatus of the present embodiment, the position of the beam spot 13 can be controlled by the method described above. Next, the beam spot 13 was moved to the narrowed portion 12 and recording was actually performed. In this example, a semiconductor laser with a wavelength of 630 nm was used, the conductor layer 2 was formed of Au, the distance between the recording head 3 and the information recording medium 7 was 10 nm, and near-field recording was performed.

  When a recording magnetic field having a frequency of 3.14 MHz was applied to the conductor layer 2 (constriction portion 12) at a position having a radius of 25 mm from the center of the information recording medium 7, and light of 5 mW was irradiated from the light source 4, ML = 0.5 μm. A record mark could be recorded. As a result, it has been found that the positions of the beam spot 13 and the constriction 12 can be accurately controlled.

  As described above, according to the present embodiment, the positional relationship between the beam spot 13 and the narrowed portion 12 is determined by comparing the position error signal from the conductor layer 2 and the position error signal from the information recording medium 7. It can be controlled precisely.

  Further, the X type and the Y type can be selectively used, or both can be used simultaneously. For example, when detecting the boundary in the X direction between the conductor layer 2 and the information recording medium 7, a Y type detection method is used, and when detecting the boundary in the Y direction between the conductor layer 2 and the information recording medium 7, the X type detection method is used. Use. If both the X type and the Y type are used, the detection accuracy can be improved. Thus, since the boundary can be accurately detected by any of these methods, for example, the distance such as the width of the conductor layer 2 can be accurately measured. Therefore, the irradiation position of the beam spot can be accurately controlled.

  If, for example, an increase / decrease in signal amplitude is detected with reference to a position error signal at the time when the beam spot 13 and the constricted portion 12 coincide with each other and feedback is performed by the head drive unit 9, the coincidence between the beam spot 13 and the constricted portion 12 occurs. It is also possible to maintain the positional relationship.

  Further, as described above, the direction in which the beam spot 13 is moved is a direction orthogonal to the direction of the edge of the conductor layer 2 (the direction of the boundary between the conductor 2 and the information recording medium 7) or the direction of the edge. Parallel direction. Also, the relationship between the direction of movement of the reflected light when detecting the reflected light of the beam spot 13 (the direction of movement of the reflected light accompanying the movement of the beam spot 13) and the direction of the substantial dividing line of the light receiving portion of the photodiode. No matter whether the photodiode is divided into two or four, the direction of movement of the reflected light is set in a direction perpendicular to the direction of the substantial dividing line. The substantial direction of the dividing line means, for example, the direction of the dividing line when a four-divided photodiode is used as a two-divided photodiode by combining a light receiving unit.

  As described above, according to the configuration of the present embodiment, the positional relationship between the beam spot 13 and the narrowed portion 12 can be accurately controlled even when the distance between the conductor layer 2 and the information recording medium 7 is wide.

  Further, the positional relationship between the beam spot 13 and the constricted portion 12 is detected by detecting, for example, increase / decrease in signal amplitude based on the position error signal when the beam spot 13 and the constricted portion 12 coincide with each other and performing feedback by the head driving unit 9. Can also be sustained.

  In the above description, the beam spot 13 is initially present on the conductor layer 2 as an example. However, even when the beam spot 13 initially exists on the information recording medium 7 or on the boundary between the conductor layer 2 and the information recording medium 7 and the position error signal is detected, the beam spot 13 is similarly based on the position error signal. Thus, the beam spot 13 can be moved to the narrowed portion 12.

  In the present embodiment, the focus point is first adjusted to the conductor layer 2 having a higher reflectance than the information recording medium 7. As a result, a position error signal having a larger signal amplitude can be obtained. However, it is obvious that the position can be controlled by the same method even when the focus point is set to the information recording medium 7.

  In any of the above examples, the position error signal is the same signal as the focus error signal. Therefore, it is possible to integrate the position control system and the focusing control system. In this case, the device structure can be simplified.

  If the amount of light reflected from the conductor layer 2 and the information recording medium 7 is also measured at the same time, more precise position control is possible. Since the reflectance of the conductor layer 2 is higher than that of the information recording medium 7, the amount of reflected light from the conductor layer 2 is larger. Accordingly, since a difference appears in the amount of reflected light depending on the position of the beam spot 13, precise position control can be performed by adding this difference to the position error signal.

  Further, in order to reproduce the information recorded on the information recording medium 7, a magnetic sensor may be used, or reflected light from the information recording medium 7 may be used. When using a magnetic sensor, the magnetic sensor may be provided at a position where recorded information in the vicinity of the constricted portion 12 can be reproduced. When using reflected light, a magneto-optical reproduction signal detection system for detecting the Kerr rotation angle from the reflected light may be provided in the optical head 6.

  Further, the shape of the narrowed portion 12 is not limited to this. It is only necessary to provide a constricted portion 12 that generates a magnetic field, and if near-field light can be generated from the constricted portion 12, the density can be further increased.

  The objective lens 5 is not necessary if the objective lens 5 can obtain an amount of light that can be recorded without condensing the light from the light source.

  In each of the above embodiments, the recording head 3 is moved based on the position error signal. However, the optical head 6 can also be moved.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The present invention can be used in a recording / reproducing apparatus that performs recording, reproduction, or erasing using light and a magnetic field such as magnetic recording, light-assisted magnetic recording, and magneto-optical recording.

It is a schematic diagram which shows the recording / reproducing apparatus in one Embodiment of this invention. It is a schematic diagram which shows an example of a structure of the optical head shown in FIG. It is a block diagram which shows an example of a structure of the position control part shown in FIG. 4A is a front view when the recording head shown in FIG. 1 is viewed from the side facing the information recording medium, and FIG. 4B is a narrowed portion in the conductor layer shown in FIG. 4A. It is an enlarged view of the vicinity. 5A is a schematic diagram showing a state in which light is applied to the conductor layer in the recording / reproducing apparatus shown in FIG. 1, and FIG. 5B shows a state in which the information recording medium is irradiated with light. FIG. 5C is a schematic view when the optical head is viewed from the information recording medium side in the state shown in FIG. 5A, and FIG. 5D is the view shown in FIG. It is a schematic diagram when the optical head is viewed from the information recording medium side in the state. 6A is a waveform diagram showing a position error signal obtained when the conductor layer is irradiated with light in the recording / reproducing apparatus shown in FIG. 1, and FIG. 6B is a waveform diagram showing light on the information recording medium. It is a wave form diagram which shows the position error signal obtained when it is irradiated. 7A is a schematic diagram showing a case where the beam spot is located on the boundary between the conductor layer parallel to the X-axis direction and the information recording medium in the recording / reproducing apparatus shown in FIG. 1, and FIG. FIG. 7 is an explanatory view of a position error signal detection principle diagram in the recording / reproducing apparatus shown in FIG. 1, and FIG. 7C is a position error signal obtained when the beam spot is at the position 15 in FIG. FIG. 7D is a waveform diagram of a position error signal obtained when the beam spot is at the position 19 in FIG. 8A is an explanatory diagram showing a state in which the beam spot is located on the conductor layer in the recording / reproducing apparatus shown in FIG. 1, and FIG. 8B is a diagram showing the beam spot from the position in FIG. 8A. FIG. 8C is a diagram illustrating a state where the conductor layer has moved on the boundary parallel to the Y-axis direction of the information recording medium. FIG. 8C shows a state where the beam spot has moved from the position of FIG. 8B onto the information recording medium. FIG. 8D is an explanatory diagram showing a state in which the beam spot has moved from the position of FIG. 8C onto the boundary parallel to the Y-axis direction between the conductor layer and the information recording medium. FIG. 8E is an explanatory diagram showing a state in which the beam spot has moved from the position of FIG. 8D to a boundary parallel to the X-axis direction between the conductor layer and the information recording medium, and FIG. Is moved from the position shown in FIG. 8E onto another boundary parallel to the X-axis direction between the conductor layer and the information recording medium. FIG. 8 (g) is an explanatory view showing a state where the beam spot is moved between the second convex portions of the conductor layer from the position of FIG. 8 (f), and FIG. FIG. 9 is an explanatory diagram showing a state in which the beam spot has moved from the position of FIG. 8G to the constricted portion of the conductor layer. FIG. 9A shows a position error signal when the beam spot is at the position of FIG. 8A when the position error signal is obtained from the conductor layer and the information recording medium of the recording / reproducing apparatus shown in FIG. FIG. 9B is a waveform diagram of a position error signal when the beam spot is at the position of FIG. 8B, and FIG. 9C is the waveform spot of the beam spot at the position of FIG. FIG. 9D is a waveform diagram of the position error signal when the beam spot is at the position shown in FIG. 8D. FIG. 9E is a waveform diagram of the position error signal when the beam spot is shown in FIG. FIG. 9F is a waveform diagram of a position error signal when the beam spot is at the position of FIG. 8F, and FIG. 9G is a waveform diagram of the position error signal when the beam spot is at the position of FIG. Waveform diagram of the position error signal when the beam spot is at the position shown in FIG. Figure 9 (h) is a waveform diagram of the position error signal when the beam spot is in the position of FIG. 8 (h). FIG. 10A is a waveform diagram of a position error signal when a position error signal is obtained only in the conductor layer of the recording / reproducing apparatus shown in FIG. 10 (b) is a waveform diagram of a position error signal when the beam spot is at the position of FIG. 8 (b), and FIG. 10 (c) is a position error when the beam spot is at the position of FIG. 8 (c). 10D is a waveform diagram of the position error signal when the beam spot is at the position of FIG. 8D, and FIG. 10E is the position of the beam spot at FIG. 8E. FIG. 10 (f) is a waveform diagram of the position error signal when the beam spot is at the position of FIG. 8 (f), and FIG. 10 (g) is a waveform diagram of the beam spot. FIG. 1 is a waveform diagram of a position error signal in the case of 8 (g). (H) are waveform diagram of the position error signal when the beam spot is in the position of FIG. 8 (h). FIG. 11A shows the case where the beam spot is located on the boundary between the conductor layer parallel to the X-axis direction and the information recording medium and the conductor layer parallel to the Y-axis direction in the recording / reproducing apparatus shown in FIG. FIG. 11B is a schematic diagram showing the case where the beam spot is located on the boundary between the information recording medium and the information recording medium. FIG. 11B shows the X type when the beam spot is at the position 15 in FIG. FIG. 11C is a waveform diagram of the Y-type position error signal of FIG. 11A. FIG. 11C shows the X-type position error when the beam spot is at the position 19 in FIG. 11A and the Y-type position error when the beam spot is at the position 102. The waveform diagram of the signal, FIG. 11 (d), shows the position error signal of the X type when the beam spot is at the position 101 or 102 in FIG. 11 (a) and the Y type when the beam spot is at the position 15 or 19. It is a waveform diagram. FIG. 12A shows a beam spot when the position error signal from the conductor layer and the information recording medium of the recording / reproducing apparatus shown in FIG. 1 is detected by the X type using a four-division photodiode. FIG. 12B is a waveform diagram of the position error signal when the beam spot is at the position of FIG. 8B, and FIG. 12C is a waveform diagram of the position error signal when the beam spot is at the position of FIG. FIG. 12D is a waveform diagram of the position error signal when the beam spot is at the position of FIG. 8C. FIG. 12D is a waveform diagram of the position error signal when the beam spot is at the position of FIG. 12 (e) is a waveform diagram of a position error signal when the beam spot is at the position of FIG. 8 (e), and FIG. 12 (f) is a position error when the beam spot is at the position of FIG. 8 (f). The waveform diagram of the signal, Fig. 12 (g), shows the beam spot. FIG. 12H is a waveform diagram of the position error signal when the beam spot is at the position of FIG. 8H. FIG. 13A shows a beam spot when the position error signal from the conductor layer and the information recording medium of the recording / reproducing apparatus shown in FIG. 1 is detected by the Y type using a four-division photodiode. FIG. 13B is a waveform diagram of the position error signal when the beam spot is at the position of FIG. 8B, and FIG. 13C is a waveform diagram of the position error signal when the beam spot is at the position of FIG. FIG. 13D is a waveform diagram of the position error signal when the beam spot is at the position of FIG. 8C. FIG. 13D is a waveform diagram of the position error signal when the beam spot is at the position of FIG. 13 (e) is a waveform diagram of a position error signal when the beam spot is at the position of FIG. 8 (e), and FIG. 13 (f) is a position error when the beam spot is at the position of FIG. 8 (f). The waveform diagram of the signal, Fig. 13 (g), shows the beam spot. FIG. 13 (h) is a waveform diagram of the position error signal when the beam spot is at the position of FIG. 8 (h).

Explanation of symbols

1 Substrate 2 Conductor layer (conductor part)
DESCRIPTION OF SYMBOLS 3 Recording head 4 Light source 5 Objective lens 6 Optical head 7 Information recording medium 8 Position control part 9 Head drive part (moving means)
10 Light leakage 12 Constriction
13, 15, 19 Beam spot 14 Photodiode 16 Object 18 Objective lens 21 Electrode part 22 First convex part 23 Second convex part 30 Collimating lens 31 Beam splitter 32 Condensing lens 40 Detection part (detection means)
41 determination unit (determination means)
42 Control unit (control means)
100 4-division photodiode

Claims (19)

An optical head that collects and emits light emitted from a light source; and a recording head that applies a current to the conductor and applies a magnetic field generated from the conductor to an information recording medium. A recording / reproducing apparatus for recording information on an information recording medium,
A moving means for relatively moving an irradiation position of light from the optical head and a position of the recording head;
A detection means for the for the light emitted from the optical head, and generates a detection signal based on the reflected light from the information recording medium and light reflected from the conductor portion of the recording head,
Determination means for determining an irradiation position of light from the optical head based on the detection signal;
Recording means comprising: control means for controlling the moving means so that the irradiation position of the light from the optical head matches the position of the conductor portion based on the determination result of the determining means Playback device. An optical head for condensing and irradiating light emitted from a light source; and a recording head for applying a current to a conductor having a constriction and applying a magnetic field generated from the constriction to an information recording medium. A recording / reproducing apparatus that irradiates light from a head to the narrowed portion and records information on an information recording medium,
A moving means for relatively moving an irradiation position of light from the optical head and a position of the recording head;
A detection means for the for the light emitted from the optical head, and generates a detection signal based on the reflected light from the information recording medium and light reflected from the conductor portion of the recording head,
Determination means for determining an irradiation position of light from the optical head based on the detection signal;
Control means for controlling the moving means so that the irradiation position of the light from the optical head and the position of the constricted portion of the conductor portion coincide with each other based on the determination result of the determining means. A recording / reproducing apparatus.   The determination unit determines the light irradiation position based on an amplitude of a detection signal detected from the conductor and an amplitude of a detection signal detected from the information recording medium. The recording / reproducing apparatus described in 1. Said determination means, the irradiation position of the light, according to claim 1, wherein the determining based on the shape of the detection signal detected from the shape and the information recording medium of the detection signal detected from the conductor portion or 2. The recording / reproducing apparatus according to 2.   The recording / reproducing apparatus according to claim 1, wherein the reflectance of the reflected light is higher in the conductor portion than in the information recording medium.   The recording / reproducing apparatus according to claim 2, wherein the narrowed portion is smaller than a diameter of a light spot from the optical head irradiated to the narrowed portion.   The recording / reproducing apparatus according to claim 2, wherein the recording head includes a near-field generating element that generates a near-field from the narrowed portion. An optical head that collects and emits light emitted from a light source; and a recording head that applies a current to the conductor and applies a magnetic field generated from the conductor to an information recording medium. Is a method of controlling a light irradiation position in a recording / reproducing apparatus for recording information on an information recording medium,
And generating a detection signal based on the reflected light from the on light emitted from an optical head, the information recording medium and light reflected from the conductor portion of the recording head,
Determining an irradiation position of light from the optical head based on the detection signal;
Relatively moving the light irradiation position from the optical head and the position of the recording head so that the light irradiation position from the optical head matches the position of the conductor portion based on the determination result And a light irradiation position control method in a recording / reproducing apparatus. An optical head for condensing and irradiating light emitted from a light source; and a recording head for applying a current to a conductor having a constriction and applying a magnetic field generated from the constriction to an information recording medium. A method of controlling a light irradiation position in a recording / reproducing apparatus that irradiates light from a head onto the conductor and records information on an information recording medium,
And generating a detection signal based on the reflected light from the on light emitted from an optical head, the information recording medium and light reflected from the conductor portion of the recording head,
Determining an irradiation position of light from the optical head based on the detection signal;
Based on the determination result, the irradiation position of the light from the optical head and the position of the recording head are relative to each other so that the irradiation position of the light from the optical head matches the position of the narrowed portion of the conductor portion. And a step of moving the light irradiation position in the recording / reproducing apparatus.   10. The recording / reproducing according to claim 8, wherein the light irradiation position is determined based on an amplitude of a detection signal detected from the conductor part and an amplitude of a detection signal detected from the information recording medium. A method for controlling a light irradiation position in an apparatus. Recording according to the irradiation position of the light, to claim 8 or 9, characterized in that determination based on the shape of the detection signal detected from the shape and the information recording medium of the detection signal detected from the conductor portion A position control method of a light irradiation position in a reproducing apparatus. Reflectance of the reflected light, the position of the irradiation position of the light in the recording and reproducing apparatus according to claim 8 or 9 towards the reflectance of the conductive portion may be higher than the reflectance of said information recording medium Control method.   10. The position control method of the light irradiation position in the recording / reproducing apparatus according to claim 9, wherein the narrowed portion is smaller than a diameter of a light spot from the optical head irradiated to the narrowed portion.   The detection means includes a light receiving element that receives the reflected light and performs photoelectric conversion, the light receiving element has a light receiving surface divided into a plurality of parts, and the determination means moves the reflected light in the detection means. 3. The recording / reproducing apparatus according to claim 1, wherein an irradiation position of light from the optical head is determined based on an amplitude of a detection signal from each light receiving surface divided in a direction.   15. The recording / reproducing apparatus according to claim 14, wherein a light receiving surface of the light receiving element is divided into four.   The determination means knives the two light receiving surfaces of the light receiving element in the detecting means into two sets of two light receiving surfaces arranged in a direction orthogonal to the direction of movement of the received reflected light as one set, 16. The recording / reproducing apparatus according to claim 15, wherein an irradiation position of light from the optical head is determined based on an amplitude of a detection signal from light received by each of the light receiving surfaces.   The conductor portion has a plurality of edge portions extending in directions orthogonal to each other, and the control means moves the light irradiation position in a direction perpendicular to and parallel to the direction of the edge portion of the conductor portion. And the light receiving element of the detecting means is parallel to at least one of the two directions which are directions of movement of the reflected light accompanying the movement of the irradiation position of the light in the two directions. 15. The recording / reproducing apparatus according to claim 14, further comprising a light receiving surface divided in a direction.   A light receiving element that has a plurality of light receiving surfaces and performs photoelectric conversion is used, and based on the amplitude of the detection signal from each light receiving surface divided in the moving direction of the reflected light in the light receiving element, the light from the optical head The light irradiation position control method according to claim 8, wherein the irradiation position is determined.   The light-receiving element has a light-receiving surface divided into four parts, and the four light-receiving surfaces of the light-receiving element have two light-receiving surfaces arranged in a direction orthogonal to the direction of movement of the received reflected light. 19. The light according to claim 18, wherein the light irradiation position from the optical head is determined based on the amplitude of the detection signal from the light received by the light receiving surfaces of the sets. Method of controlling the irradiation position of the.

Images