JPS61255547A - Optical-magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To improve the S/N and quality of a reproduction signal by providing a laser beam source and a positional detector on the same base of an optical head, and providing a signal detector and a signal processing circuit on a base for signal processing that is separated from the former one. CONSTITUTION:When the beams from an objective lens 14 properly form an image on the recording plane of an optical-magnetic recording medium 30, the said image-formation, the emitting point of the source 10, and an image- formation on the positional detector 17 are in conjugate relation. Therefore, if the positional relation between the source 10 and the detector 17 is maintained constant, a correct error-signal is at all time obtained, and accurate automatic focus control and track servo control are executed. Meanwhile, a reproduction signal separated by a polarizing beam splitter enters the signal detector 22 by spatial propagation. Because the detector 22 is provided together with the signal processing circuit 22 including the primary amplifier on the base for signal processing that is provided separately from the base of optical head 1, the S/N and the quality of the reproduction signal are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to magneto-optical recording and reproducing technology, which performs recording and reproduction by magnetizing a magnetic thin film by photothermal means and detecting the state of magnetization on the magnetic thin film using the Kerr effect. It relates to the main device, especially its signal reproduction system.

2. Description of the Related Art A conventional magneto-optical recording/reproducing apparatus has a structure shown in FIGS. 6 and 7, as described in, for example, Technical Research Report CPM83-ts3 of the Institute of Electronics and Communication Engineers. That is, in FIG. 7, the light emitted from the laser light source 1o passes through the collimator lens 11 and becomes parallel light, and then passes through the half mirror (
) IM) 12, passing through the total reflection mirror 13 to the objective lens 1
4 and is focused on the recording surface of the magneto-optical recording medium 30 (FIG. 6). The next light reflected by the magneto-optical recording medium 30 is HM1
2 and enters a polarizing beam splitter (PBS) 15. PBSls are optical elements whose transmittance or reflectance varies depending on the polarization direction of light incident thereon. When light hits the magneto-optical recording medium 30, the direction of polarization of the reflected light is slightly rotated according to the polarity of magnetization of the recording surface (Kerr effect). The rotation of the polarization angle can be detected as a change in light intensity by the analyzer 21, which has the function of passing only light polarized in a certain direction, and furthermore, the signal can be detected as an electrical signal by the signal detection detector 22. can do.

However, in general, the Kerr rotation angle is very small, about ±0.5°, and the intensity ratio is less than 2 inches. The PB 816 serves to substantially increase the polarization angle difference of the light incident on the analyzing element 21. In other words, most of the components in the polarization direction specific to the saw light source 2 1Q are reflected by the PBSls, and all the light in the direction perpendicular thereto, that is, newly generated due to Kerr rotation, is transmitted. The transmitted light with a polarization angle difference is transmitted to an analyzing element 2 and a signal detection detector 22.
The polarization angle difference is converted into an electrical signal and sent to the subsequent signal processing circuit 23.

The reflected light from which the polarization angle difference has been almost completely removed is further HMle
and one side is divided into focus error detection lenses 18.
and one is extracted as an electrical focus error signal by the position detection detector (focus error detection detector) 17a, and one is extracted as an electrical tracking error signal by the position detection detector (tracking error detection detector) 1abVc. Both of these are sent to the automatic focus control and track following control circuits.

Problems to be Solved by the Invention However, these conventional techniques have had the following problems. In other words, the magneto-optical reproduction signal is very weak and does not account for even 20% of the light reflected by the magneto-optical recording medium 30. As mentioned earlier, PBSls increases the Kerr rotation angle, but this only increases the modulation rate by cutting the unique polarization component of the laser light source 1o, which corresponds to the DC bias, and the signal detection based on the DC bias Although the shot noise of the detector 22 is reduced and the S/N ratio is improved somewhat, the reproduced signal level remains unchanged.

Such weak electrical signals are greatly affected by noise generated within the first stage amplifier. In particular, since the connection cable 4o, which itself has no amplification effect and is susceptible to the influence of induced noise, connects the signal detection detector 22 and the signal processing circuit 23, the resulting reduction in S/N becomes a problem.

Although it is possible to improve the S/N by making the connection cable 40 as short as possible, the magneto-optical recording/reproducing apparatus generally moves the optical head base 1 including the position detecting detector 22 as shown in FIG. Since the information surface is scanned, the length of the connection cable is required to be at least as long as the stroke length of the optical head base 1.

Means for Solving the Problems In order to solve these problems, the present invention provides a laser light source and a position detection detector on the optical processing board.

As a result, the connection cable connecting the signal detection detector and the signal processing circuit is eliminated, and the optical head base and the signal processing base are optically connected, thereby eliminating the above-mentioned problem.

Embodiment FIG. 1 is a block diagram of main parts showing an embodiment of the present invention. In FIG. 1, a laser light source 10 and a position detection detector 1
7 is provided on the optical head base 1, and a signal detection detector 22 and a signal processing circuit 23 are provided on the signal processing base 2. The reception and delivery of signals from the optical head base 1 to the signal processing base 2 is performed by allowing the light reflected from the magneto-optical recording medium 3o to propagate in space as it is.

This configuration will be explained below. Generally, an optical head performs automatic focus control and automatic track following control in response to time changes in the position of the recording medium, and an error signal representing positional deviation that is input into the control loop is generated by an optical system including a position detection detector 17. To detect. If there is an error in this error signal itself, these controls may not be performed correctly, and writing/reproducing operations on the magneto-optical recording medium 30 may not be possible. When the light emitted from the objective lens 14 is correctly imaged on the recording surface (reflection surface) of the magneto-optical recording medium 30, the image formation, the light emitting point of the laser light source 10, and the image formation on the position detection detector 17 are in an image conjugate relationship with each other, so the laser light source 1o and the position detection detector 1
7. If the mutual positional relationship is kept unchanged, a correct error signal can always be obtained. However, to avoid this, the laser light source 10 and the position detection detector 1a must be firmly fixed on the same base so that the positional relationship between them does not shift. The same applies to the no-f mirror (HM) 12 and the polarizing beam splitter (PBS) 16.

On the other hand, the reproduced signal light separated by PBSls is allowed to have some deviation as long as it enters the signal detection detector 22, regardless of the above-mentioned position control. Rather, as mentioned earlier, the S/N of the reproduced signal is a problem, so the signal detection detector 2
2 is a signal processing board 2 provided separately from the optical head board 1;
It is better to provide it together with a signal processing circuit including a first-stage amplifier at the top.

As a result, the signal detection detector 22 and the signal processing circuit 2
3 can be omitted, making it less susceptible to induced noise.

Other embodiments of the present invention will be described below. FIG. 2 is a perspective view showing a second embodiment of the present invention, and FIG. 3 is a configuration diagram thereof. In FIG. 3, an optical head base 11L1, a laser light source 10. Collimator lens 11, HM12, total reflection mirror 13, objective lens 14, PBSls, HM1θ,
Focus error detection lens 18, position detection detector 17a.

The function and structure of 1Tb are exactly the same as those of the conventional example.

The signal detection detector 22, signal processing circuit 23, and signal processing board 2 have the configuration described in the first embodiment.

In this embodiment, an analyzer element 21 is also provided on the signal processing board 2 in order to make the optical head board 1 simpler and lighter. 24
is a convex lens whose purpose is to increase the tolerance for positional errors between the optical head base 1 and the signal processing base 2 by widening the aperture area.

FIG. 2 shows a type of magneto-optical recording and reproducing apparatus in which the optical head base 1 can move in the same way as FIG. If the direction of the optical axis is set in the same direction, the signal processing board 2
can always receive the reproduced signal light from the optical head base 1.

Even if the optical head base 1 is displaced due to mechanical play or the like, there will be no effect as long as the optical axis of the reproduced signal light does not protrude significantly from the signal detection detector 22.

Furthermore, in this embodiment, a part of the signal processing circuit 23 is covered with a shield plate 26 except for the vicinity of the optical path of the reproduced signal light, which protects the circuit part that is particularly susceptible to the influence of induced noise from induced noise. It was established for the purpose of

Next, a third embodiment of the present invention will be described. FIG. 4 is a perspective view showing a third embodiment of the present invention. In FIG. 4, an optical head base 1 is provided on a signal processing base 2. In FIG. Scanning of the information plane is performed by moving the objective lens 14 in the optical axis direction. This type of drive mechanism is known (Japanese Unexamined Patent Publication No. 15534/1983).

An advantage of applying the present invention to this type of magneto-optical recording/reproducing device is that the circuit board can be easily arranged. In the conventional case, the circuits that must be installed near the optical head board 1 are not only the first stage amplifier of the signal processing circuit 23, but also the modulation circuit of the laser light source 10 used for writing operations, the first stage amplifier of the servo circuit, etc. It is. Furthermore, in the signal processing circuit 23, it is desirable that not only the first-stage amplifier but also digital circuits such as a digital demodulation circuit and an error correction circuit be placed on the same circuit board, which inevitably increases the circuit scale.

However, by applying the present invention, this problem can be solved by creating a configuration as shown in FIG. That is, since the optical head board 1 and the signal processing circuit 23 are connected by optical communication, the signal processing circuit 23 does not necessarily need to be provided near the optical head board 1. Rather, as described above, it is more convenient to arrange other circuits 26 that need to be provided nearby near the optical head base 1 and to arrange the signal processing circuit 23 at an appropriate location.

Effects of the Invention The present invention provides a laser light source and a position detection detector on the same optical head base, and a signal detection detector and a signal processing circuit on a signal processing base separate from the optical head base, thereby reducing induced noise. It is possible to obtain a magneto-optical recording and reproducing device that is not easily affected and can obtain a reproduction signal of commercial quality.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of the main part of an embodiment of the present invention, and FIG.
3 and 3 are respectively a perspective view and a configuration diagram showing a second embodiment of the present invention, FIG. 4 is a perspective view showing a third embodiment of the invention, and FIG. 5 is a diagram for explaining the same. 6 and 7 are a perspective view and a configuration diagram of a conventional example. DESCRIPTION OF SYMBOLS 1... Optical head base, 10... Laser light source, 17... Position detection detector, 2.
... Signal processing base, 22 ... Signal detection detector, 23 ... Signal processing circuit, 14 ...
...Objective lens, 16...Polarizing beam splitter (PBS). Name of agent: Patent attorney Toshio Nakao and 1 other person
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Claims (5)

[Claims] (1) A laser light source, an objective lens that focuses the light emitted from the laser light onto a magneto-optical recording medium, and an electrical a position detection detector that outputs an output to the magneto-optical recording medium, an analyzer that detects the polarization angle of the light reflected or transmitted from the magneto-optical recording medium as optical intensity, and converts the light that has passed through the analyzer into an electrical signal. A magneto-optical recording/reproducing device equipped with a signal detection detector, wherein the laser light source and the position detection detector are provided on an optical head base, and the signal detection detector amplifies at least an electric signal obtained from the signal detection detector. 1. A magneto-optical recording and reproducing device, characterized in that the optical head base and the signal processing base are provided separately from each other, and the optical head base and the signal processing base are provided on a signal processing base together with a signal processing circuit having a function. (2) The magneto-optical device according to claim 1, characterized in that at least a part of the signal processing circuit is covered with a conductive casing, except for the vicinity of the optical path of the light incident on the signal detection detector. Recording and playback device. (3) The magneto-optical recording and reproducing apparatus according to claim 1, wherein the analyzing element and the signal detection detector are provided on a signal processing board. (4) The magneto-optical recording and reproducing apparatus according to claim 1, further comprising a convex lens provided on the signal processing board and in the optical path of the light incident on the signal detection detector. (5) The magneto-optical recording and reproducing apparatus according to claim 1, wherein the signal processing base is fixed, and the optical head base is movable relative to the signal processing base.