JPH01169762A - Optical head for real time erasing of recording - Google Patents

Abstract

PURPOSE:To erase/record in real time by providing plural light sources, a collimator lens, a beam splitter, a condensing lens, an analyser to detect a positional error signal, and a light receiving element to convert light flux to an electrical signal. CONSTITUTION:Three beams of diffusing light from the light source part 1 are made parallel beams by the collimator lens 3, linearly polarized by the beam splitter 4, and condensed as fine spots on the surface of a disk 2 by the condensing lens 5. A light beam reflected on the surface of the disk 2 passes through the lens 5 again, reflected by the splitter 4, transmits through a 1/2-wavelength plate 6, and made incident to the composite analyser 7. A focus error signal 11 is detected from the light beam reflected by a half mirror 7 among the light beams 17 for servo incident to the analyser 7b. A tracking error signal 14 is detected out of a light beam 17 made incident to the photodetective element 9b. A reproduced signal 13 is obtained from a signal outputted from the photodetective elements 8a, 9a through differential reproduced signal detecting system.

Description

Detailed Description of the Invention [Industrial Application Field 1] The present invention relates to an optical head for real-time recording and erasing in a magneto-optical disk device, and in particular, to a 7↑-scatter error detection Wi function and a differential power system to obtain a reproduction signal. The present invention relates to an optical head for real-time recording and erasing that has both functions and a composite analyzer.

[Prior Art] In general, a magneto-optical disk drive uses an optical head equipped with a light source that emits a single diffused beam of light to condense and irradiate the light beam from the light source onto the disk in the form of a minute light spot, thereby generating information. Recording and playback are in progress.

Among these magneto-optical disk devices, a schematic configuration of a magneto-optical disk device using a differential reproduction signal detection method is shown in FIG. In the figure, 2o is a magneto-optical disk (hereinafter referred to as a disk), 21 is a motor that rotates the magneto-optical disk, and 22 is a motor that rotates the magneto-optical disk.
is a semiconductor laser which is modulated by the input signal 35 and emits a plurality of diffused lights. 23.28.31 is a condensing lens, 2
4 is a beam shaping prism, and 25.27 is a beam splitter (polarizing beam subrifter) which reflects the reflected light beam from the disk 2 ( ) and divides it into nine parts. A condensing lens 26 condenses the light passing through the beam splitter 25 toward the disk 20 onto the disk 20 as a light spot. Two analyzers (for magneto-optical use) detect the Kerr rotation angle (described in detail later) of the reflected light beam from the disk 20 that has passed through the beam splitter 25, 27. 30. 32 is a photodetector, the photodetector 30 detects the light flux passing through the analyzer 29,
The photodetector 32 detects a light beam containing error information such as a 7-orcus error reflected from the disk 20 and converts it into an electrical signal. Reference numeral 33 denotes an objective lens driving device that finely adjusts and corrects the condensing lens X using a signal from the photodetector 32. 3
Reference numeral 4 denotes an electromagnet for applying an external magnetic field, which applies a magnetic field to a portion of the disk 2G that includes the spot.

In the magneto-optical disk device having the above configuration, when recording is performed, the disk 20 is magnetized with negative polarity, and the laser beam from the semiconductor laser 22 is directed onto the disk 20 through the objective lens 2G to form a special spot and 15. When irradiated, the temperature of the irradiated area rises 1-1. When it reaches the Curie point, magnetization reversal occurs. In this state, the electromagnetic 534
Therefore, when a magnetic field in the opposite direction to the previous magnetic field is applied to the light spot portion, only the spot portion is magnetized downward. In this way, by changing the direction of magnetization of the disk 20 depending on whether or not the laser beam is irradiated onto the disk 20, information in the form of digital values of 1" and "0" is recorded.

Furthermore, to erase the information recorded on the disk 20, the electromagnet 34 applies an external magnetic field in the direction in which the disk 20 was initially magnetized, which is opposite to the case of binary recording, and irradiates a light spot. be struck by something.

On the other hand, when reproducing recorded information, there is a phenomenon called the Kerr effect, in which when linearly polarized incident light is reflected on the surface of a magnetized medium, the azimuth of the reflected light is tilted by a predetermined angle. phenomenon is used. In other words, when the laser beam from the semiconductor laser 22 is linearly polarized by the beam splitter 25 and is incident on the magnetic film on the disk 20, the azimuth of this reflected light is changed by the Kerr effect, and when the recording signal is 1'', +θk (Kerr rotation angle),'0
'', the rotation angle is detected by the analyzer 29 and the information recorded on the disk 20 is reproduced.

[Problem to be Solved by the Invention 1] In the above-mentioned magneto-optical disk device of the differential reproduction signal detection method, erasing and recording operations are performed separately. That is, in order to record again after recording has been carried out over the entire area of the disk 20, the recording operation must be performed after erasing the entire area of the disk 20 (making the direction of magnetization the same), and the recording operation is performed in real time. There was a problem that it could not be erased or recorded.

Therefore, a magnetic field direct modulation method was devised as one of the methods to solve this problem, but high-speed recording was difficult due to the inductance of the electromagnet used. Another method is a two-head force type, but this has problems such as complicating the system and increasing costs.

The present invention has been made to solve the above-mentioned conventional drawbacks, and aims to provide an optical disc for real-time recording and erasing that is capable of erasing and recording information in real time and has a simple configuration. .

Means for Solving Problem E] In order to solve the above problem, the present invention provides a plurality of light sources that individually emit a plurality of diffused lights including at least a recording diffused light and an erasing diffused light, and this light source. A collimator lens converts the diffused light emitted from the beam into parallel light, and a beam splitter 2 converts a plurality of incident light beams into linearly polarized light and reflects the reflected light beam from the recording medium surface. An analyzer for detecting a reproduction signal and a position error signal of the Moe condenser lens from the light beam reflected from the condenser lens and the +if beam splitter, which converge the light as a plurality of light spots on the surface of the recording medium. and,
A light receiving element was provided to convert the luminous flux emitted from the analyzer into an electrical signal.

[Operation 1] In the above configuration, the plurality of diffused lights emitted from the individual light sources are made into parallel lights by the frimeter lens, and then enter the beam splitter, and each light beam is made into FIi-line polarized light. The light beam emitted from the beam splitter is focused by a condenser lens onto the surface of the recording medium as a plurality of light spots. Therefore, by providing a plurality of light sources that include at least recording diffused light and erasing diffused light and emit these separately, erasing and recording can be performed in real time. Furthermore, among the plurality of reflected light beams from the recording medium surface, those due to the reproduction diffused light and those due to the servo diffused light are reflected by the beam splitter via the condenser lens and enter the analyzer. Each light beam divided by the analyzer enters a light receiving element and is converted into an electrical signal. As a result, a reproduction signal and a position error signal of the condenser lens are detected from the light beam incident on the analyzer.

[Example] Hereinafter, an example of the present invention will be described with reference to Fig. f51 to Fig. 3.

FIG. 1 is a schematic diagram of an optical head for real-time recording and erasing showing one embodiment of the present invention. In the figure, 1 is a light source section that has, for example, three semiconductor lasers 1 at 1 b and 1 c and individually emits diffused light, 2 is a magneto-optical disk (hereinafter referred to as disk) which is a recording medium, and 3 is a collimator. A lens converts the diffused light from the light yi section 1 into parallel light. 4 is a beam splitter, which converts the incident light beam into linearly polarized light and reflects the light beam reflected from the two surfaces of the disk in the right angle direction.6 5 is a condenser lens, which focuses the incident light beam into a minute spot on the two disk surfaces. do. 6 is a 1/2 wavelength plate, which changes the polarization plane of the light beam reflected from the beam splitter 4 to 90
Rotate degrees. Reference numeral 7 denotes a composite analyzer, which includes a convex lens 7a for condensing an incident light flux as a minute spot on each light-receiving element (to be described later), an analyzer 7b, and a knife formed by vapor-depositing metal or the like. It is composed of a film (IQ that blocks a semicircular portion of the luminous flux) 7c. 8 and 9 are light receiving elements, and the individual light receiving elements 8 a, 8 b,
Consisting of 8 c and 9 a, 9 b, 9 c,
The light flux from the composite analyzer 7 is converted into an electrical signal.

Reference numeral 10 denotes an electromagnet for applying an external magnetic field, which applies a magnetic field to a minute spot irradiated onto the disk 2.

The three semiconductor lasers 1a, 1b of the light source section 1,
In this embodiment, 1 c is a servo light beam 1 for detecting a position error signal of the condenser lens 4, for example.
7. A light source that emits an erasing light beam 18 and a recording/reproducing light beam 19. Then, a focus error signal 11, a track address signal 12, and a tracking error signal 14 are detected from the servo light beam 17. Further, a reproduction signal 13 is detected from the recording/reproducing light beam 19. Note that the recording/reproducing light beam 19 may be obtained from an independent light source, and the servo light beam 17 may also be used as the erasing light beam 18.

FIGS. 2(a) and 2(b) are detailed views of the composite analyzer 7 shown in FIG. 1, where (a) is a perspective view, and FIG. It is a front view seen from the direction. Same figure (a)
, (b), arrow B indicates the incident direction of the luminous flux, and arrows C and D indicate the output direction of the luminous flux. 7d is a half-mirror surface of the analyzer 7, and the incident light beam passes through this half-mirror surface 7d.
The light beam is divided into two light beams emitted in the direction of arrow C and the direction of arrow C.

, 11. The knife [97c] provided on the exit surface of the light beam in the arrow direction is for detecting the focus error signal of the condenser lens X4 using a knife f-foot set from the servo light beam 17.

The operation of this embodiment with the above configuration will be explained below.

The three diffused lights from the light source section 1 are made into parallel lights by the collimator lens 3, and then enter the beam splitter 4. The incident light flux is made into linearly polarized light by this beam splitter 7 and transmitted straight through, and j! The light is focused by the lens 4 on the surface of the disk 2 as a minute spot. The light beam reflected on the surface of the disk 2 passes through the optical lens 4, is reflected by the beam splitter 4, passes through the 1/2 wavelength plate 6, and enters the composite analyzer 7.

Incidentally, the servo light beam 17 reflected from the two surfaces of the disk and incident on the composite analyzer 7 is used to detect the position error signal of the condenser lens 7::5.

The focus error signal 11, which is one of the error signals of the condenser lens 5 (i! passes through the tip nA (edge part) of the knife ill 7c and enters the light receiving element 8b.The knife method is used to detect this focus error signal 11 as described above.This knife method is When the condensing lens 5 is in focus with no 7 orcus error, the light beam becomes narrowest (the light beam forms an image) at the position of the knife lens 7c, and the light beam is not blocked at all by this eye film 7c. Convex Shin 7
Since the dimensions of each member such as :7a are set, when a 7 orcus error occurs in the condenser lens The light receiving element 8b detects 72 balances of light amounts and outputs a focus error signal 11.

Also, among the position error signals, tracking error signal 1
4 enters the composite analyzer 7, passes through the half mirror surface 7d without being reflected, and is detected from the servo light beam 17 that enters the light receiving element 9b. In this case, a push-pull method is adopted.

Note that a track address signal 12 is obtained from the focus error signal 11 and the tracking error signal 14.

Furthermore, the reproduced signal 13 will be explained. Recording/playback light beam 1
9 is reflected by the disk 2 surface, further reflected by the beam splitter 4, enters the composite analyzer 7, and is split into two beams by the half mirror surface 7d, which are transmitted to light receiving elements 8a and 9a.
are incident on each.

A reproduced signal 13 is obtained from the signal output from the light receiving element 8 at 9 a by a differential reproduced signal detection method. This differential reproduction signal detection method utilizes the polarization characteristics of the reproduction signal 13 to produce the effect of reducing noise caused by changes in the amount of light.

Next, the operation of erasing and recording in real time will be explained with reference to FIG. FIG. 3 is a partially enlarged view showing the main part of the surface of the magneto-optical disk 2. As shown in FIG. In the figure, 20 is a bit row, 15 is a pre-group part which is a guide groove, and 16 is a land part where information is recorded. positive integers not including O). The minute spot of the servo light beam 17 runs through the pregroup section 15, and the minute spot (hereinafter, "minute spot" will be omitted) of the recording/reproduction light beam 19 runs along run 1='g16.

Next, the operation of the erasing light beam 18 will be explained. For example, record
If the reproducing light beam 19 runs on the land portion 16 of the innermost track 21(1), the erasing light beam 18 runs on the land portion 16 of the track 21(2). In general, records and
When the reproducing light beam 19 runs on the land portion 16 of the track (nl), the erasing light beam 18 runs on the land portion 16 of the track 21 (n).

At this time, the magnetic fields applied by the electromagnet 10 (see FIG. 1) to the portion of the recording/reproducing light beam 19 and the portion of the erasing light beam 18 on the disk 2 surface have opposite polarities. That is, since the erasing light beam 18 always runs ahead of the land portion 16 of the outer track 21 (n) adjacent to the track 21 (n-1) on which the servo light beam 17 is running, no data is recorded on this land portion 16. The information that has been saved will be deleted. Therefore, for example, the servo light beam 17 goes around the track 21(1), and then goes around the track 21(2).
When running on the track 21(2), the land portion 16 of the track 21(2) is erased as described above, so this track 21(2)
is in a recordable state, and at this time, information can be written and recorded immediately in real time.

By the way, if you want to start recording again from the beginning on a disc 2 that has been completely recorded, as described above, the land portion 16 of the innermost track 21 (1) of the disc 2 (the track where recording starts) has not been erased and cannot be recorded on this track 21(1), so the outer track 2 adjacent to this innermost track 21(1)
It is first necessary to wait until the disk 2 completes one rotation until the land portions 16 of 1 (2) are erased and placed in a recordable state. However, since the rotational speed of this disk 2 is relatively high, the problem of time loss can be ignored.

In this embodiment, three light sources are provided and three diffused lights are used as the recording/reproducing, servo, and erasing light beams, respectively, but other combinations are also possible. For example, the erasing light beam 18 can also be used as the reproduction light beam 19.

Further, recording and erasing can be performed in real time if at least separate light sources for recording and erasing are provided, and therefore, a case in which there are two light sources is also conceivable.

Furthermore, when re-recording on the disc 2 using the above method and reproducing it, the recording prior to re-recording remains in the innermost track 21(1). Therefore,
In order to solve this problem, the track 21(1) at the innermost circumference of the disk 2 is provided with only a pre-group portion 15 (a guide groove for the servo light beam 17) and without a land portion 16, and is used for recording. By configuring the structure so that the recording is not possible, it is possible to prevent the recording from before the re-recording from being left on the innermost track 21 (1,) of the disc 2 when re-recording the disc 2 from the beginning. .

[Effect of the Invention 1] As explained above, the present invention includes a light source that emits a plurality of diffused lights, a collimator lens that converts the diffused lights into parallel lights, and a beam splitter that reflects the reflected light beam from the recording medium surface. , a condensing lens that condenses the light beam onto the surface of the Moekki 41 medium, an analyzer that detects a reproduction signal and a position error signal of the condenser lens, and a light receiver that converts the light beam into an electrical signal. Since the configuration is equipped with an element, it has become possible to erase and record information in real time with a relatively simple configuration.

In addition, by using a composite analyzer in which a convex lens is bonded to the analyzer and a two-knife film is formed, an extremely simple optical system with a small number of parts can be achieved even when using a differential reproduction signal detection method. I was able to do this.

[Brief explanation of the drawing]

tIS1 is a schematic diagram of an optical head for real-time recording/erasing showing an embodiment of the present invention, Figures 2 (a) and (b) are detailed diagrams of a composite analyzer according to the present invention, and Figure 3 is a magneto-optical head. FIG. 4 is a partially enlarged view showing essential parts of the surface of a disk, and FIG. 4 is a schematic diagram showing a conventional magneto-optical disk device. DESCRIPTION OF SYMBOLS 1... Light source part, 2... Magneto-optical disk, 3... Collimator lens, 4... Beam splitter, 5... Condensing lens, 6... 1/2
Wave plate, 7... Composite analyzer, 7a... Convex lens, 7
b...Analyzer, 7c...Two knife membranes,
8, 9... Light receiving element, 10... Magnetic head, 11.
... Focus error signal, 12... Track address signal, 13... Reproduction signal, 14... Tracking error signal, 17... Light flux for servo, 18... Light flux for erasure,
19...Light flux for recording/reproduction.

Claims (2)

[Claims] (1) A plurality of light sources that individually emit a plurality of diffused lights including at least a recording diffused light and an erasing diffused light, a collimator lens that converts the diffused light emitted from the light sources into parallel light, and a plurality of incident light beams. a beam splitter that converts each into linearly polarized light and reflects the reflected light flux from the recording medium surface; a condensing lens that focuses the light flux that has passed through the beam splitter as a plurality of light spots on the recording medium surface;
an analyzer for detecting a reproduction signal and a position error signal of the condenser lens from the light beam reflected from the beam splitter; and a light receiving element for converting the light beam output from the analyzer into an electrical signal. An optical head for real-time recording and erasing. (2) The analyzer is a composite in which a convex lens for forming a light spot on the light-receiving element is adhered to the incident surface of the light beam, and a knife edge film is formed on the exit surface of the light beam for obtaining a focus error signal. The optical head for real-time recording and erasing according to claim 1, which is an analyzer.