Magnetooptical information recording/reproducing apparatus and method using magnetic head

Abstract: Recording of information on and/or reproduction of information from a magnetooptical recording medium is effected as follows. Light beam from an objective lens is irradiated on a track of the recording medium. The objective lens is driven in a direction perpendicular to the track such that the beam spot and the track have a predetermined positional relationship therebetween. A magnetic field modulated according to information to be recorded is applied to the beam spot irradiated position of the recording medium by magnetic field applying device. A relative position between the objective lens and the magnetic field applying device in the direction perpendicular to the track is detected. The recording of information is effected on the recording medium by applying the magnetic field according to the information while changing the beam spot irradiated position on the recording medium with respect to the track. The movable range of the objective lens, in which a level of a reproduction signal obtained in the reproduction of information exceeds a predetermined level, in the direction perpendicular to the track, in the recording operation, is detected on the basis of a detection result of the relative position, so that a driver for the objective lens is controlled on the basis of the detected movable range.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a magnetooptical information recording/reproducing apparatus and method, which can erase and rewrite information on a disk-shaped magnetooptical recording medium and, more particularly, to a magnetooptical information recording/reproducing apparatus and method corresponding to a magnetic field modulation type overwrite-capable magnetooptical recording medium. Related Background Art Conventionally, the performance of a magnetooptical recording method based on a magnetic field modulation method has been sufficiently improved so as to achieve short recording, reproduction, and erase times, a large capacity, and high-speed access. Such a magnetooptical information recording/reproducing apparatus reflecting the preamble of the independent claims has a construction, as shown in, e.g., Fig. 1. More specifically, seek operations of both an optical head (optical pickup device) 103 and a magnetic head 108 are simultaneously performed by a seek motor. The seek motor is constituted by a linear motor coil 104 provided on the optical head 103, and a magnetic circuit arranged along a guide 107 for guiding the optical head 103 and including a magnet 106 and a yoke 105. The magnetic head 108, which opposes the optical head 103 to sandwich a recording medium therebetween, is mounted on a floating slider. The slider is mounted on a coupling member 110 via a support beam (suspension) 109, and the coupling member 110 is fixed to the optical head 103. The optical head 103 comprises an actuator 102 for two-dimensionally driving its objective lens 102a, and can finely adjust the tracking and focusing directions of the objective lens 102a. A seek operation in the radial direction of a magnetooptical recording medium 101 is attained by current control for the linear motor coil 104, as described above, and tracking and focusing operations in recording and reproduction modes are attained by current control for a corresponding coil of the actuator 102. In this case, the tracking control of the objective lens 102a by the actuator 102 is limited to a movable range of the objective lens 102a. When a tracking error is large, and exceeds the movable range, tracking control of the optical head 103 itself is performed using the above-mentioned seek motor. However, in the above-mentioned construction, the relative position between the optical head 103 and the magnetic head 108 must be adjusted with high precision since it influences data reproducibility of magnetooptical recording media compatible to a magnetooptical disk apparatus. Thus, the apparatus must be assembled with strict care. However, since the magnetic head 108 is mechanically coupled to the optical head side via the support beam (suspension) 109, it is difficult to adjust the apparatus with required precision, and such adjustment requires considerable time. When the apparatus is used, a change in volume of the mechanical coupling portion occurs due to a change in temperature in the apparatus, and this may shift the relative position between the optical head 103 and the magnetic head 108. In this manner, when the relative position adjustment precision is lowered, recording may be performed to disturb data reproducibility even within the fine adjustment movable range of the objective lens 102a by the actuator 102. EP-A-0464947 discloses a device for writing and/or reading a magnetooptical disc. The device includes a control system for determining during operation of the device, the radial position of the optical unit and the magnetic unit relative to each other and for controlling the radial position of the coil within the magnetic unit relative to the objective lens within the optical unit. Patent Abstracts of Japan, Vol 14, No. 165 (p-1030) and JP-A-2021444 discloses a magnetooptical head device including separately movable optical and magnetic heads. Means are provided for maintaining the relative positions of the optical and magnetic heads. Patent Abstracts of Japan, Vol 13, No. 424 (p-934) and JP-A-1155504 discloses a magnetooptical head in which the optical head and magnetic head are separate. Means is provided for preventing shifting of the radiation spot produced on the magnetooptic medium and the magnetic head. Patent Abstracts of Japan, Vol 14, No. 482 (p-1119) and JP-A-2193346 discloses a magnetooptical head in which the optical head and the magnetic head are driven individually. Feedback control is used to align the radiation beam and magnetic field at the required positions on the recording medium. Patent Abstracts of Japan, Vol 13, No. 322 (p-902) and JP-A-1089054 discloses a magnetooptical device including separately driven magnetic and optical heads. In order to align the optical and magnetic heads a servo amplifier is used. SUMMARY OF THE INVENTION The present invention has been made in consideration of the above situation, and has as its object to provide a magnetooptical information recording/reproducing apparatus and method, which can prevent recording, which may disturb data reproducibility, even when relative position adjustment between a magnetic head and an optical head is insufficient upon assembling of the apparatus and/or when the relative position adjustment precision is lowered due to, e.g., a change in temperature in the apparatus. According to a first aspect of the present invention there is provided a method for performing at least one of the functions of recording and reproducing information on or from a magnetooptical recording medium, said method comprising the steps of: irradiating a track of the recording medium using an objective lens to produce a beam spot on the recording medium; detecting the deviation of the beam spot from the track and generating a tracking error signal; and executing tracking control of the beam spot by driving the objective lens on the basis of the tracking error signal; the method being characterized in further comprising the steps of: applying a magnetic field modulated by test information to the recording medium at the position of the beam spot while varying the position of the beam spot on the recording medium transversely to the track by moving the objective lens, so as to effect recording of test information on the medium; reproducing the test information recorded on the recording medium to produce a reproduction signal; detecting the range of movement of the objective lens in the direction perpendicular to the track during said test information recording step, for which the detected reproduction signal exceeds a predetermined level; and performing said tracking control of the beam spot on the basis of the detected range of movement. According to a second aspect of the present invention there is provided an apparatus for performing at least one of the functions of recording and reproducing information on or from a magnetooptical recording medium, the apparatus comprising: means including an objective lens for irradiating a track of the recording medium with a beam spot; means for detecting the deviation of the beam spot from the track and for generating a tracking error signal; and means for executing tracking control of the beam spot by driving the objective lens on the basis of the tracking error signal; the apparatus being characterized in further comprising: a magnetic field applying means for applying a magnetic field modulated by test information to the recording medium at the position of the beam spot; means for moving the objective lens so as to vary the position of the beam spot on the recording medium transversely to the track, thereby to effect recording of test information; reproduction means for reproducing the test information recorded on the recording medium to produce a reproduction signal; means for detecting the range of movement of the objective lens in the direction perpendicular to the track during the recording of the test information, for which the level of the detected reproduction signal exceeds a predetermined level; and control means for controlling the tracking control means on the basis of the detected range of movement. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view showing a conventional magnetooptical information recording/reproducing apparatus; Fig. 2 is a perspective view showing a magnetooptical information recording/reproducing apparatus according to the first embodiment of the present invention; Fig. 3 is an enlarged perspective view of an optical pickup device in the apparatus shown in Fig. 2; Fig. 4 is a circuit diagram of a position sensor in the device shown in Fig. 3; Fig. 5 is a graph showing the output characteristics of the circuit shown in Fig. 4; and Fig. 6 is a block diagram showing a control system of the magnetooptical information recording/reproducing apparatus according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In a magnetooptical information recording/reproducing apparatus shown in Fig. 2, both an optical head (optical pickup device) 6 for irradiating a recording medium with a beam spot and a magnetic head (not shown) arranged on a floating slider 4 are mounted on a single carriage, and their seek operations are simultaneously performed by a seek motor. The seek motor is constituted by a linear motor coil 9 provided to the optical head 6, and a magnetic circuit arranged along a guide rail 8 for guiding the optical head 6 and including a magnet 10, a center yoke 12, a back yoke 11, and joint yokes 13 for coupling these yokes. The slider 4 is attached to a pivot member 14 of a magnetic head escaping mechanism via a support beam (suspension) 5. The pivot member 14 is supported on the optical head 6 to be pivotal about a support shaft 15. An escaping control roller 14a is attached to the rear end of the pivot member 14. A drive member (not shown) of the escaping mechanism, which member has a pressing surface extending in the seek direction, is arranged to oppose the control roller 14a from the above so as to push the control roller 14a downward. The optical head 6 has an objective lens 2 facing the magnetic head, and also has an actuator 3 for finely moving and adjusting the objective lens 2 in the tracking and focusing directions. As shown in detail in Fig. 3, in the actuator 3, opposing back yoke portions 26a are formed on the right and left portions of a yoke 26 also serving as a mounting substrate, and magnets 25 are mounted on the back yoke portions 26a. A lens holder 21, which holds the objective lens 2, is arranged between these magnets 25. Tracking coils 24 and focusing coils 23 are attached to the lens holder 21 to oppose the magnets 25. A spacer 27 is arranged at one side of the yoke 26 to be located on the back surface of one back yoke portion 26a. Leaf springs 22 extend from the spacer 27 in the back-and-forth direction of the lens holder 21 to movably support the lens holder 21 in the back-and-forth direction (tracking direction). For this reason, when the coils 24 are energized, the lens holder 21 is finely moved and adjusted in the tracking direction. In this embodiment, a flat detection end member 22a is cut and stands upright from one leaf spring 22, and a lens position sensor 28 is attached to the yoke 26 via a bracket so as to sandwich the detection end member 22a from its right and left sides. As shown in Fig. 4, the lens position sensor 28 comprises an LED 31 and a phototransistor 32 which oppose each other to sandwich the detection end member 22a therebetween. The LED 31 and the phototransistor 32 are connected to a power supply V cc via resistors 33 and 34, respectively, and an output terminal (OUTPUT) of the sensor 28 is connected to an arithmetic circuit 41 (Fig. 6). Note that the phototransistor has characteristics shown in Fig. 5, and the ratio of the photoelectric current value when the end position of the detection end member 22a is separated by L mm from the center of the lens position sensor is specified. For this reason, when the objective lens 2 (in other words, the lens holder 21) is finely moved and adjusted in the tracking direction, since the photoelectric current value changes, the position of the objective lens 2 relative to the carriage in the tracking direction can be detected. This means that the relative position between the objective lens 2 and the magnetic head or the relative position between a beam spot and the magnetic head can be detected. A control system of the magnetooptical information recording/reproducing apparatus has a construction, as shown in the schematic diagram of Fig. 6. In this arrangement, a system controller 44 serves as a central control unit. A magnetooptical recording medium 1 is rotated by driving a spindle motor 35 via a servo control circuit 43 in response to an instruction from the system controller 44, and a servo signal can be output to the coils 23 via a focusing drive circuit 36, to the coils 24 via a tracking drive circuit 37, and to the linear motor coil 9 via a linear motor drive circuit 38. On the other hand, as for an optical system, a laser driver 39 is driven in response to an instruction signal from the system controller 44. In the optical system, a servo signal and a data signal are extracted from light reflected by the magnetooptical recording medium 1 via a servo/RF amplifier 40. The servo signal is fed back to the servo control circuit 43 to attain tracking/focusing control of a beam spot, and the data signal is output to an encoder/decoder 46 as a reproduction signal or a verify signal in a recording mode. The system controller 44 performs laser irradiation onto the recording surface of the magnetooptical recording medium using the optical system on the basis of data information input from an external apparatus via the encoder/decoder 46, and applies a modulated magnetic field to the magnetic head on the basis of the data signal supplied from the encoder/decoder 46 to a magnetic head drive circuit 45, thus realizing magnetooptical recording. In particular, according to the present invention, a test signal is supplied from the control system to the encoder/decoder 46 to record the test signal prior to recording on the magnetooptical recording medium 1, and at the same time, a reproduction signal of the recorded test signal is detected by the servo/RF amplifier 40. When the test signal is recorded, the system controller 44 performs recording while driving the objective lens 2 from one end to the other end of the movable range via the servo control circuit 43. The servo control circuit 43 checks the amplitude level of the detected reproduction signal, and controls the arithmetic circuit 41 to calculate the movable range (a range capable of assuring an application magnetic field necessary for recording) in which information whose amplitude level exceeds a predetermined level is recorded, in the tracking direction, of the objective lens 2 in the recording mode, on the basis of the output from the position sensor 28, and to store the movable range in a memory (storage means) 42. Upon execution of data recording, the servo control circuit 43 limits tracking control, so that the tracking control of the objective lens 2 is performed within the movable range stored in the memory 42. When magnetooptical recording is performed on a magnetooptical recording medium 1 compatible to the magnetooptical information recording/reproducing apparatus in this manner, the tracking fine adjustment range of the objective lens 2 in the recording mode can be limited, and data reproducibility in a reproduction mode can be assured even when the relative position between the magnetic head and the optical head is aligned with poor precision in assembling and/or when a position error occurs in use. In the data reproduction mode, the above-mentioned limitation is canceled, and fine adjustment of the objective lens is performed within a range allowed by the actuator 3 and wider than that in the recording mode, thus improving near-seek performance. [Second Embodiment] In the first embodiment, a movable range, in which the amplitude level of a reproduction signal becomes equal to or higher than a predetermined level, of the objective lens 2 is detected, and in the data recording mode, the tracking control of the objective lens 2 is limited to fall within the movable range. However, in the second embodiment, the central position of a movable range, in which the amplitude level of a reproduction signal becomes equal to or higher than a predetermined level, of the objective lens 2 is obtained, and a shift amount between the central position and an initial position of the objective lens 2 is detected. In the data recording mode, the tracking control of the objective lens 2 may be performed while being shifted by the detected shift amount. The second embodiment will be described in detail below using the construction of the first embodiment described above. In the second embodiment, a test signal is supplied from the control system to the encoder/decoder 46 to record the test signal prior to recording on the magnetooptical recording medium 1, and at the same time, a reproduction signal of the recorded test signal is detected by the servo/RF amplifier 40. When the test signal is recorded, the system controller 44 performs recording while driving the objective lens 2 from one end to the other end of the movable range via the servo control circuit 43. The servo control circuit 43 checks the amplitude level of the detected reproduction signal, and controls the arithmetic circuit 41 to calculate the central position of the movable range (a range capable of assuring an application magnetic field necessary for recording) in which information whose amplitude level exceeds a predetermined level is recorded, in the tracking direction, of the objective lens 2 in the recording mode, on the basis of the output from the position sensor 28, to further calculate a shift amount (offset amount) between the calculated central position and a reference position (neutral position or initial position) of the objective lens 2 with respect to the optical head 6, and to store the shift amount in the memory (storage means) 42. Upon execution of data recording, the servo control circuit 43 executes tracking control of the objective lens 2 to shift the movable range by the offset amount stored in the memory 42. More specifically, the servo control circuit 43 adds or subtracts the offset amount to or from a servo signal obtained via the servo/RF amplifier 40, and executes the tracking control of the objective lens 2 using the servo signal obtained as a result of the calculation. In place of shifting the tracking control range of the objective lens 2 by the offset amount, eccentric tracking (control for driving the optical head using the seek motor so that the objective lens 2 is located at the reference position of the optical head 6) of the optical head 6 with respect to tracks on the magnetooptical recording medium 1 may be performed while being shifted by the offset amount stored in the memory 42, thus obtaining the same effect as described above. Note that the shift operation is performed to compensate for the offset amount. When magnetooptical recording is performed on a magnetooptical recording medium 1 compatible to the magnetooptical information recording/reproducing apparatus in this manner, data reproducibility in a reproduction mode can always be assured within the tracking fine adjustment range of the objective lens 2 even when the relative position between the magnetic head and the optical head is aligned with poor precision in assembling and/or when a position error occurs in use.

Claims: A method for performing at least one of the functions of recording and reproducing information on or from a magnetooptical recording medium (1), said method comprising the steps of: irradiating a track of the recording medium using an objective lens (2) to produce a beam spot on the recording medium (1); detecting the deviation of the beam spot from the track and generating a tracking error signal; and executing tracking control of the beam spot by driving the objective lens (2) on the basis of the tracking error signal; the method being characterized in further comprising the steps of: applying a magnetic field modulated by test information to the recording medium (1) at the position of the beam spot while varying the position of the beam spot on the recording medium (1) transversely to the track by moving the objective lens (2), so as to effect recording of test information on the medium (1); reproducing the test information recorded on the recording medium (1) to produce a reproduction signal; detecting the range of movement of the objective lens (2) in the direction perpendicular to the track during said test information recording step, for which the detected reproduction signal exceeds a predetermined level; and performing said tracking control of the beam spot on the basis of the detected range of movement. A method according to claim 1, wherein said tracking control step is performed so that the objective lens (2) is moved within only said detected range of movement. A method according to claim 1, wherein said tracking control step includes the steps of: determining the center position of the detected range of movement; calculating the difference between the center position and an initial position of the objective lens (3); and adding a signal representative of the calculated difference to the tracking error signal. A method according to any one of claims 1 to 3 in which said tracking control step is performed whilst recording data on the recording medium (1). A method according to any one of claims 1 to 3 in which the tracking control step is performed during reproduction of data recorded on the recording medium (1). An apparatus for performing at least one of the functions of recording and reproducing information on or from a magnetooptical recording medium (1), the apparatus comprising: means including an objective lens (2) for irradiating a track of the recording medium (1) with a beam spot; means (28) for detecting the deviation of the beam spot from the track and for generating a tracking error signal; and means (37) for executing tracking control of the beam spot by driving the objective lens (2) on the basis of the tracking error signal; the apparatus being characterized in further comprising: a magnetic field applying means for applying a magnetic field modulated by test information to the recording medium (1) at the position of the beam spot; means for moving the objective lens (2) so as to vary the position of the beam spot on the recording medium (1) transversely to the track, thereby to effect recording of test information; reproduction means (40) for reproducing the test information recorded on the recording medium (1) to produce a reproduction signal; means (44, 28) for detecting the range of movement of the objective lens (2) in the direction perpendicular to the track during the recording of the test information, for which the level of the detected reproduction signal exceeds a predetermined level; and control means (41, 42, 43) for controlling the tracking control means (37) on the basis of the detected range of movement. An apparatus according to claim 6, wherein said means for tracking control means is arranged to control the movement of the objective lens (2) to be within only the detected range of movement. An apparatus according to claim 6, including: means for determining the center position of the detected range of movement; means for calculating the difference between the center position and an initial position of the objective lens (2); and means (41) for adding the calculated difference to the tracking error signal. An apparatus according to any one of claims 6 to 8, including means for recording data on said track. An apparatus according to any one of claims 6 to 9 including means for reproducing data recorded on said track.

Inventors: FUJINO MASAHISA, FUJINO, MASAHISA, Fujino, Masahisa, c/o Canon Kabushiki Kaisha
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1993
Main classification: G11B11
IPC codes: G11B11