JP2551762B2 - Information storage device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention modulates a light beam such as a laser beam or an electron beam with an information signal and irradiates it on a storage medium to store, reproduce or erase information. The present invention relates to an information storage device that performs the above.

[Prior Art] Typical examples of the information storage device as described above include an optical disk device represented by a video disk and an optical card device recently. The basic tracking error detection method used in the optical disk device will be described below with reference to the conventional example shown in FIG.

In FIG. 3, DSK is an optical disc in which pits are recorded, and a beam splitter BS for guiding the reflected light from the optical disc DSK to the two-divided photodetector TDPD along the optical path of the laser beam emitted from the semiconductor laser LDI. , A collimator lens CL, and an objective lens SL for focusing the laser beam on a spot of about 1 μmφ on the optical disc DSK are arranged. A two-divided photodetector TDPD is provided in the reflection direction of the beam splitter BS, and its output signal is input to the differential amplifier DA.

In such a configuration, if the pit PIT on the optical disc DSK is shifted to the right of the laser beam spot LBS as shown in FIG. 4 (a), the photodetector TDPDL of the left half of the two-divided photodetector TDPD is
The amount of received light increases, and conversely, as shown in (b), the pit PIT
Is closer to the left side of the spot LBS, the amount of light received by the photodetector TDPDR in the right half portion increases. As shown in (c), when the pit PIT is correctly located at the center of the spot LBS, the photodetectors TDPDL and TDPDR on the left and right have the same amount of light received. Therefore, by comparing the left and right outputs of the two-divided photodetector TDPD, it is possible to detect the position shift amount and shift direction of the pit PIT and the spot LBS, and the signal differentially amplified by the differential amplifier DA is tracked. Used as signal TES.

However, with the method of obtaining a tracking error signal using a laser beam represented by a conventional example, it is difficult to reduce the diameter of the spot LBS to 1 μmφ or less, so it is possible to obtain a more accurate tracking error signal TES in the future. This cannot be expected, and therefore it is difficult to perform high-density recording with the track pitch further reduced from the current 2 μm.

Further, in such a method using a laser beam, a large number of high-precision optical components such as a beam splitter and a lens are used, so that the cost is very high and a large volume is required. Furthermore, since the S / N ratio of the tracking error signal TES generally obtained by such a method is low, a relatively sophisticated technique is required for signal processing, and highly accurate positioning of individual optical components is required. Is. Also,
When the laser beam is finally moved minutely on the pit PIT, it is performed by mechanically moving the optical parts by the actuator, so there is a limit to the response frequency, which is also a large factor for high-precision tracking. It is an obstacle.

[Object of the Invention] An object of the present invention is to provide an information storage device capable of obtaining a highly accurate tracking error signal by using an electron beam which can easily obtain a minute spot and has high controllability.

[Summary of the Invention] The gist of the present invention for achieving the above object is to provide a device for forming a spot on a storage medium by a beam and performing at least any one of recording, reproduction and erasing of information in the storage. A reference pattern made of a conductor is provided on the medium, a source of a tracking electron beam is provided facing the reference pattern, and a current flowing through the reference pattern is detected by irradiating the reference pattern with the tracking electron beam. The information storage device is provided with a detecting means for obtaining a positional deviation detection signal.

[Embodiment of the Invention] The present invention will be described in detail with reference to the embodiments shown in FIGS. 1 and 2.

In FIG. 1, MM is a storage medium, and a source MEBD of an electron beam MEB for storing / reproducing / erasing information is arranged above the storage medium. In this example, the source MEBD
Is an element in which a plurality of electron beam sources are densely arranged in one dimension. For example, JP-B-54-30274, JP-A-54-11272, JP-A-56-15529, and JP-A-57-38528. And the like. Since the electron beam generation source MEBD can easily change the current density of each electron beam MEB, the current density is increased at the time of recording or erasing information to change the material of the storage medium MM and to cause the pit PIT. It can form and disappear. In addition, when reproducing information, it is possible to reproduce the information without lowering the current density and changing the material of the storage medium MM. Therefore, as the material of the storage medium MM, amorphous is crystallized by electron beam irradiation. Ge (11.5), Te (57.5), As (31), etc. are used which cause a phase change that makes the crystal amorphous. An electron beam source TEBD for tracking is provided on the side of the electron beam source MEBD.
BD generates a tracking electron beam TEB having a diameter of about 0.2 μm. In this case, the current density of the tracking electron beam TEB is so low that the tracking spot TEBS formed on the storage medium MM does not change the material of the storage medium MM.

Further, on the storage medium MM, there are provided tracking reference patterns PL and PR composed of two parallel conductors facing in the x direction, and the electron beams from the tracking electron beam generation source TEBD are provided in these patterns PL and PR. Electric current is made to flow by irradiation of TEB, and two reference patterns PL and PR
Is about 0.1 μm. Lead wires LLL and LLR that lead out currents are connected to the reference patterns PL and PR, and these output currents are converted into voltages and connected to a differential amplifier DA via amplifiers AL and AR, respectively. Differential amplifier DA is an amplifier
The output difference between AL and AR is amplified, and the amount of current flowing through the reference patterns PL and PR is compared by this output. The output from the differential amplifier DA passes through the phase compensation circuit PRC and the driver T
It is connected to a CD. The output of the driver TCD is applied to deflection electrodes TCR and TCL that generate a uniform electric field for simultaneously deflecting the tracking electron beam TEB and a plurality of information recording / reproducing / erasing electron beams MEB in the y direction.
The driver TCD deflects the deflection electrode TCR when the current flowing in the reference pattern PL is larger than the current flowing in the reference pattern PR.
The voltage is applied to the deflection electrodes TCR and TCL according to the output of the differential amplifier DA such that the voltage is positive and TCL is negative. The application of this voltage causes the deflection electrode TCR to become negative and TCL to become positive when the current flowing through the reference pattern PL is smaller than the current flowing through the reference pattern PR in accordance with the output of the differential amplifier DA. SCD is a drive circuit that generates a voltage in accordance with the signal SL1, the output of which is connected to the deflection electrodes SC1 and SC2, and the tracking electron beam TEB and a plurality of electron beams MEB for recording / reproducing / erasing information. Are simultaneously generated in the x direction to generate a uniform electric field. A signal SL2 for recording and partial erasing is input to the electron beam generation source MEBD, and the electron beam generation source MEBD generates an electron beam MEB modulated by the signal SL2. Most of the components shown in FIG. 1 are housed in a vacuum vessel (not shown).

In such a configuration, when the tracking beam spot TEBS has a relationship with the reference patterns PL and PR as shown in FIG. 2A, comparing the currents flowing in the reference patterns PL and PR, the electron beam TEB irradiation is performed. Since a larger current flows in the reference pattern PL having a large amount, a voltage is applied so that the deflection electrode TCR is positive and the deflection electrode TCL is negative as described above, and the tracking electron beam TEB is deflected by the deflection electrode TCR.
The beam spot TEBS is deflected to the side and moves from the reference pattern PL side to the PR side. At this time, the plurality of electron beams MEB for storing / reproducing / erasing information are also deflected under the influence of the same electric field as that of the tracking electron beam TEB.

On the other hand, when the tracking beam spot TEBS and the reference patterns PL and PR have the relationship shown in FIG.
When the currents flowing in the reference patterns PL and PR are compared, a larger current flows in the reference pattern PR having a large irradiation amount of the electron beam TEB, so that the deflection electrode TCR has a negative voltage and TCL has a positive voltage as described above. Is applied, the tracking electron beam TEB is deflected to the deflection electrode TCL side, and the beam spot TEBS moves from the reference pattern PR side to the PL side.
Also at this time, just as in the case of FIG. 2A, the plurality of electron beams MEB used for recording / reproducing / erasing information are deflected by receiving the same electric field as the tracking electron beam TEB.

In the state shown in FIG. 2 (c), the differential amplifier DA
No voltage is applied to the deflection electrodes TCR and TCL, and neither the tracking electron beam TEB nor the plurality of electron beams MEB are deflected at all.

Deflection electrode SC during actual recording / reproducing / erasing of information
1.Change the voltage of SC2 gradually,
Thus, the spot train generated on the storage medium MM is moved in the x direction. At this time, the relationship between the tracking beam spot TEBS and the reference patterns PL and PR changes continuously as shown in FIGS. 2 (a), (b), and (c), and as a result, the relationship between FIG. The state of (c), that is, the beam spot TEBS is controlled to be located at an intermediate position between the reference patterns PL and PR.

In this embodiment, 1/1 of the diameter of the beam spot TEBS
It is possible to scan the tracking electron beam TEB along the reference patterns PL and PR with high accuracy of 0, that is, about 0.02 μmφ. Therefore, a plurality of electron beams MEB that receive the same electric field as the tracking electron beam TEB also scan with the same accuracy as the tracking electron beam TEB, and the pits recorded based on the reference patterns PL and PR are used. Reference patterns PL and PR even when playing or erasing PIT
It is possible to trace extremely accurately by scanning with the tracking electron beam TEB.

Further, in this embodiment, not only the tracking beam is the electron beam TEB, but also the beam for recording / reproducing / erasing information is the electron beam MEB. There is also an advantage that the beam can be deflected and the actuator required for the light beam is not required at all. Further, as compared with a light beam in which it is difficult to arrange a plurality of them in a high density, the electron beam does not require a deflecting means individually, so that the beam can be easily densified at a high speed.
High-density recording is possible. Further, in the present embodiment, the tracking electron beam generation source TEBD and the plurality of electron beam generation sources MEBD are separate elements for convenience of description, but in one element that generates a plurality of electron beams, one or It is also possible to employ a form in which several electron beams are used for tracking and the rest are used for recording / reproducing / erasing information.

Further, in the present embodiment, an example in which the electron beam is deflected by an electric field has been described, but it goes without saying that the same effect can be obtained by deflection by a magnetic field.

Although the electron beam MEB was used for recording / reproducing / erasing information, of course, the recording / reproducing / erasing of this information may be performed by a light beam, and the output of the differential amplifier DA is the drive of a so-called optical head tracking actuator. By using it as a signal, a tracking error signal with extremely high accuracy and a high S / N ratio can be obtained, so that it becomes possible to perform tracking with extremely high accuracy in the conventional case.

Furthermore, in the above-described embodiment, the electron beams TEB and MEB can be easily deflected in the x direction in FIG. 1, so an example in which the storage medium MM is not intentionally moved has been described, but in the present invention, the storage medium moves. The tracking error signal detecting means is more effective for a medium such as an optical disk or an optical card that moves and rotates because it has high followability to the vibration caused by Becomes

As described above, according to the information storage device of the present invention, the beam tracking error signal is detected by detecting the current flowing in the reference pattern made of the conductor on the storage medium by the irradiation of the electron beam. Therefore, it is possible to obtain extremely high-accuracy signal detection with a high S / N ratio, and it is possible to narrow the track pitch and perform high-density recording.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of an information storage device according to the present invention,
2 is an explanatory view of the relationship between the reference pattern and the electron beam spot, FIG. 3 is a configuration diagram of a conventional tracking error signal detection method using a light beam, and FIG. 4 is a light beam spot detection element of FIG. FIG. 5 is an explanatory diagram of a light intensity distribution in FIG. Reference numeral MM is a storage medium, MEBD is an electron beam generation source, TEBD is a tracking electron beam generation source, PL and PR are reference patterns, TCL, TCR, SC1 and SC2 are deflection electrodes, and DA is a differential amplifier.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Mamoru Miyawaki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yukio Masuda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Hitoshi Oda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) Reference JP-A-60-117434 (JP, A) JP-A-53-71825 (JP , A) JP-A-54-24615 (JP, A) JP-A-60-29953 (JP, A)

Claims (4)

(57) [Claims] 1. An apparatus for forming a spot on a storage medium by a beam and performing at least one of recording, reproduction and erasing of information, wherein a reference pattern made of a conductor is provided on the storage medium, and the reference pattern is provided. A generation source of a tracking electron beam is provided opposite to the pattern, and a detection unit for detecting a current flowing through the reference pattern by irradiating the reference pattern with the tracking electron beam to obtain a position deviation detection signal is provided. A characteristic information storage device. 2. The information storage device according to claim 1, wherein the tracking electron beam is deflected together with the storage / reproduction / erasure beam. 3. The information storage device according to claim 1, wherein the reference pattern is two parallel conductors. 4. The information storage device according to claim 3, wherein the displacement detection signal is a difference signal between the two conductors.