JPS61280052A - Photomagnetic disk device - Google Patents

Abstract

PURPOSE:To eliminate the need to match the levels of two signals and to shorten a switching time by synthesizing a signal of two signals detected by different photodetectors in a digital signal state. CONSTITUTION:A photomagnetic signal detection system consists of an analyzer 10, a lens 11, and photodetector 12 and the slight rotation of a plane of polarization is converted by the analyzer 10 into variation in the quantity of light, which is detected by a photodetector 12. A servo signal and header signal detection system consists of an optical detection system 13 and a photodetector 14. A photomagnetic signal is amplified by an amplifier 15 and converted into an analog signal, which is digitized by a digitizing circuit 16. A header signal detected by another detector 14 is amplified by an amplifier 17 and a converted into an analog signal, which is digitized by a digitizing circuit 18. Those are put together and a timing signal for removing a header signal part from the photomagnetic signal is generated by passing the header signal through a timing generating circuit 19.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a magneto-optical disk device, which is a type of erasable optical disk, and particularly relates to a magneto-optical disk device that is a type of erasable optical disk, and in particular, a header signal of change in reflectance including address information, a magneto-optical signal that is data, The present invention relates to a magneto-optical disk device suitable for signal processing of a magneto-optical disk having a magneto-optical disk.

[Background of the invention]

Magneto-optical disks use a perpendicular magnetization film for the recording film, and record information with the magnetization pointing upwards or downwards.Furthermore, they are erasable, and have a large capacity.

In recent years, development has been active as a file memory that combines the features of non-contact recording and rewritability of magnetic disks. Signal detection of magneto-optical disks was proposed in a patent application filed in 1983.
As described in No. 242006, the header signal containing address information recorded in advance in the form of uneven bits on the disk and the magneto-optical signal which is data are detected using separate detectors. The magneto-optical signal is detected as a change in reflectance in the same way as for read-only and write-once optical discs, and the magneto-optical signal is detected using an analyzer as a slight rotation of the plane of polarization due to the upward and downward directions of magnetization due to the Kerr effect. This will be detected as a change in the amount of light. As described above, separate photodetectors are used due to the difference in detection principles, and conventionally, when these signals are sent to a host controller, they are mixed in the form of analog signals.

However, to mix analog signals, there are problems such as (1) the amplitude of each signal must be matched, and (2) switching in an analog manner takes too much time.

[Purpose of the invention]

An object of the present invention is to provide a magneto-optical disk device that does not have the problems of amplitude adjustment and switching time as described above.

[Summary of the invention]

The present invention is characterized in that two separately detected signals are separately digitized and then mixed.

When considering increasing the speed of magneto-optical disks, the switching time when mixing two signals cannot be ignored, and mixing after digitizing is more effective than mixing in an analog state because the switching time is shorter. .

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. Light emitted from a laser 1 (for example, a semiconductor laser) is condensed by a coupling lens 2 to become parallel light, and then transmitted to a beam splitter 3. The light passes through the galvanometer mirror 4 and is focused onto the perpendicularly magnetized film 7 on the disk 6 by the focusing lens 5 to a spot diameter of about 1 μm. In the initial state, the perpendicular magnetization film 7 is entirely magnetized upward or downward. Recording/erasing of information is usually called cue black recording, in which the perpendicularly magnetized film 7 is heated to the cue point temperature by laser beam irradiation to demagnetize it, and at the same time, an external magnetic field is applied by the electromagnetic coil 8. Recording occurs when the direction of the magnetic field is opposite to the initial state, and erasure occurs when the direction is the same. The light reflected by the perpendicular magnetization film 7 passes through the aperture lens 5. The light passes through a galvanometer mirror 4, has an optical path separated by a beam splitter 3, and is guided to a signal detection system. The signal detection system includes a magneto-optical signal detection system and a servo signal and header signal detection system, which are separated by a second beam splitter 9.

The magneto-optical signal detection system is an analyzer 10. It consists of a lens 11 and a photodetector 12, and the plane of polarization of the reflected light rotates slightly in accordance with the upward and downward magnetization of the perpendicularly magnetized film 7.
Using the err effect, this slight rotation of the plane of polarization is converted into a change in light amount by the analyzer 10, and this is detected by the photodetector 12. The servo signal and header signal detection system consists of a detection optical system 13 and a photodetector 14, which are used for ordinary video discs and audio discs, and are used to detect automatic focus detection signals and track tracking signals. A header signal pre-recorded on the disc in the form of uneven bits is detected.

The magneto-optical signal detected by the photodetector 12 and the header signal detected by the photodetector 14 have a relationship as shown in FIG. After being amplified by the amplifier 15, the magneto-optical signal is shown in Fig. 2(a).
The signal becomes an analog signal as shown in , and includes a header signal. However, at the angle of the analyzer 10 where the magneto-optical signal serving as data is at its maximum, the header signal becomes 3 to 5 times as large as the magneto-optical signal. Therefore, when this is passed through the digitization circuit 16 including a comparator circuit, it becomes a digital signal, but since the comparator level of the header signal part is different from that of the magneto-optical signal part, the header signal part cannot be used (the header signal part cannot be used). Figure 2(b)). Therefore, a header signal detected by another photodetector 14 is used.

After this signal is amplified by the amplifier 17, it is shown in Fig. 2 (C).
This is an analog signal shown in FIG. 2, and is converted into a digital signal through the digitization circuit 18 in the same way as the magneto-optical signal (FIG. 2(d)). In order to send the reproduced signal to the upper controller, it is necessary to include address information and DATA, and the signals shown in FIGS. 2(b) and 2(d) are combined. A timing signal (FIG. 2(e)) for removing the header signal portion from the magneto-optical signal is generated by passing the header signal through the timing generation circuit 19. This timing generation circuit 19 detects the sector mark included in the header signal, creates timings indicating the header signal period and data period based on this, and generates the sampling timing signal (e). The digitized magneto-optical signal (b) is extracted and the timing signal (e) is input to the AND logic element 20, whereby the header signal portion is extracted and only the data portion is left (FIG. 2(f)).

Finally, the digitized header signal (d) and the extracted magneto-optical signal (f) are input to the OR logic element 2I and sent to the upper controller as a magneto-optical signal with a header signal. In the above explanation, AN is used for extraction and synthesis of header signals.
D, an OR logic element is used, but T, which is a data selector,
Even if you use IC from company I, 5N74157, etc. (bL (
dL (e) The above-mentioned magneto-optical signal with header signal (g) can be created from each signal.

A second embodiment of the present invention will be explained with reference to FIG.

This uses differential detection as the magneto-optical signal detection system in FIG. 1, and since the components from the laser 1 to the disk 6 are the same, they are omitted. The reflected light from the disk enters the beam splitter 9, where it is guided to a header signal detection system and a magneto-optical signal detection system. As explained in the first embodiment, the header signal detection system detects the digitized header signal using the optical system 13.
．． Photodetector 14 and amplifier 17. Digitization circuit 1
8. The magneto-optical signal detection system is a 172 wavelength plate 2.
2 and a polarizing prism 23, each is detected by a combination of a lens 24, a photodetector 25, a lens 26, and a photodetector 27, and a magneto-optical signal is detected by a differential amplifier 28. . This magneto-optical signal is as shown in FIG. 4(b), and unlike the first embodiment, the header signal portion does not appear. Therefore, the header-attached magneto-optical signal to be sent to the host controller is the analog signal (b) passed through the digitization circuit 29 to be converted into a digital signal (c).

Further, it is obtained by inputting both signals (a) and (c) to an OR logic element. In this way, when detecting magneto-optical signals by differential detection, a timing circuit for extracting header signals is not required.

〔Effect of the invention〕

According to the present invention, since two signals detected by separate photodetectors are combined in a digital signal state, there is no need to adjust the levels of the two signals, and the switching time is shortened. .

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a first embodiment of the present invention, and FIG. 2 is a diagram showing a first embodiment of the present invention.
FIG. 3 is a diagram showing the second embodiment of the present invention, and FIG. 4 is a diagram showing the waveforms of each part in the second embodiment. l... Laser light source, 7... Perpendicular magnetization film, 8... Electromagnetic coil, 19... Timing generation circuit, 22...
1/2 wavelength plate, 23... polarizing prism, 28... differential amplifier. ￥J1 country

Claims (1)

[Claims] 1. A laser light source, an optical system that focuses the light from the laser light source as a minute spot on a perpendicularly magnetized film of a recording medium, and a first detection system that detects the direction of magnetization of the perpendicularly magnetized film and converts it into a change in light amount. and a second detection system for detecting a header signal recorded in advance in the form of concave and convex bits on a recording medium, in which the first detection system and the second detection system are each configured separately. 1. A magneto-optical disk device characterized by being provided with a digitizing circuit and synthesizing both signals after they have been digitized.