JP3144588B2 - Magneto-optical information reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical information reproducing apparatus for reproducing information recorded on a magneto-optical recording medium.

[0002]

2. Description of the Related Art In recent years, a magneto-optical information recording / reproducing apparatus using a magneto-optical disk as a recording medium has to be portable.
High expectations have been placed on the large storage capacity and the possibility of erasing and rewriting. FIG. 7 is a configuration diagram showing an optical system of the conventional magneto-optical information recording / reproducing apparatus. In FIG. 7, reference numeral 36 denotes a semiconductor laser serving as a recording / reproducing light source. A divergent light beam emitted from the laser 36 is collimated by a collimator lens 37 and corrected by a beam shaping prism 38 into a parallel light beam having a circular cross section. . Here, the parallel light beam is a light beam of linearly polarized light (hereinafter referred to as P-polarized light) having a polarization direction parallel to the paper surface. This P-polarized light beam enters the polarization beam splitter 39. As the characteristics of the polarization beam splitter 39, for example, linearly polarized light (hereinafter referred to as S-polarized light) having a transmittance of 60% for P-polarized light, a reflectance of 40%, and a polarization direction perpendicular to the polarization direction of P-polarized light. Has a transmittance of 0% and a reflectance of 100%. The P-polarized light flux transmitted through the polarization beam splitter 39 is condensed by the objective lens 40 and is
A light spot is formed on one magnetic layer. Further, an external magnetic field is applied from the magnetic head 42 to the light spot irradiating section, and an information magnetic domain is formed on the magnetic layer.

[0003] The reflected light from the magneto-optical disk 41 is returned to the polarizing beam splitter 39 via the objective lens 40, where a part of the reflected light is separated and brought to the reproducing optical system. In the reproducing optical system, the separated light beam is further separated by a separately prepared polarizing beam splitter 43. As characteristics of the polarization beam splitter 43, for example, the transmittance of P-polarized light is 20%, the reflectance is 80%, the transmittance of S-polarized light is 0%, and the reflectance is 100%. One of the light beams split by the polarization beam splitter 43 is guided to a reproduction optical system 44 to generate a reproduction signal as described later. The other light beam is guided to a half prism 53 via a condenser lens 52, where it is split into two, one to a photodetector 54 and the other to a photodetector 56 via a knife edge 55. Be guided. Then, these control optical systems generate servo error signals for auto-tracking control and auto-focusing control of the light beam.

The reproducing optical system 44 changes the polarization direction of the light beam to 45.
A half-wave plate 45 for rotating the beam, a condenser lens 46 for condensing the light beam, a polarization beam splitter 47, and photodetectors 48 and 49 for detecting the light beam separated by the polarization beam splitter 47, respectively. I have. As characteristics of the polarization beam splitter 47, the transmittance of P-polarized light is 100%, the reflectance is 0%, the transmittance of S-polarized light is 0%, and the reflectance is 100%. The signals detected by the photodetectors 48 and 49 are differentially detected by the differential amplifier 50 and the reproduced signal 51
Is generated. Here, in a magneto-optical recording medium, information is recorded by a difference in the direction of perpendicular magnetization.
Recording methods include an optical modulation method and a magnetic field modulation method. The light modulation method is a method of irradiating a recording medium with a laser beam modulated according to recording information while applying a constant external magnetic field. The magnetic field modulation method is a method of applying an external magnetic field modulated according to recording information while irradiating a recording medium with a laser beam having a constant intensity.

When a magneto-optical medium on which information is recorded due to the difference in the direction of magnetization is irradiated with linearly polarized light,
The polarization direction of the reflected light rotates clockwise or counterclockwise depending on the direction of the magnetization. For example, as shown in FIG. 8, the polarization direction of linearly polarized light incident on a magneto-optical recording medium is represented by a coordinate axis P.
The reflected light for the downward magnetization is R ₊ rotated by + θ _K, and the reflected light for the downward magnetization is R ₋ rotated by −θ _K.
And Therefore, placing the analyzer in a direction as shown in FIG. 8, A light whereas R ₊ coming through the analyzer, R _- to become B, and this is detected by the photodetector, the light intensity Information can be obtained as the difference. In the example of FIG. 7, the polarization beam splitter 47 serves as an analyzer, and one of the separated light beams is analyzed at +45 degrees from the P axis, and the other light beam is analyzed at −45 degrees from the P axis. Become a photon. That is, since the signal components obtained by the photodetectors 48 and 49 have opposite phases, a differentially detected individual signal can provide a reproduced signal with reduced noise.

Here, when information is recorded in pits, there are a pit position recording method in which the position of the center of the pit has the meaning of the information and a pit edge recording method in which the position of the edge of the pit has the meaning of the information. is there. FIG. 9 is a diagram for explaining both of these recording methods. FIG. 9A shows a pit row for pit position recording. The size of the pit is approximately constant at a nearby pit. 9B is a detection signal obtained by optically reproducing the pit train shown in FIG. 9A, FIG. 9C is a pit train for pit edge recording, and FIG. 9D is a pit train shown in FIG. 9C. Are optically reproduced detection signals. In order to know the position of the edge of the pit from this detection signal, for example, a slice level may be provided electrically and a position where the detection signal in FIG. 9D crosses the slice level may be obtained. FIG. 9 (e)
Indicates the edge detection signal.

When information is recorded on a magneto-optical recording medium using optical means, the size of the pits is reduced if the recording sensitivity at which the pits are written on the magneto-optical recording medium is moderate with respect to the heat generated by the light spot. Will vary. However, the position of the center of the pit does not change. Conventionally, for this reason, pit position recording is often performed in magneto-optical recording media using optical means. On the other hand, when the recording sensitivity at which the pits of the magneto-optical recording medium are written in response to the heat generated by the light spot is steep, the variation in the pit size can be reduced to a certain amount or less. Thus, the storage density can be increased. Therefore, recently, a magneto-optical recording medium suitable for pit edge recording and a pit recording method have been developed, and pit position recording has been shifted to pit edge recording.

[0008]

However, as described above, in the prior art, pit edge recording has been made possible by improving the recording medium and the like. When the distance is about the same as or smaller than the size of the light spot, a new problem arises in that the transfer characteristics of the optical head and the like deteriorate. Therefore, the DC component of the detection signal shown in FIG. 9A fluctuates, and when the detection signal is sliced at a constant slice level to detect the edge of the pit, the position of the detected edge shifts, and the information is shifted. Cannot be detected accurately.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to provide a magneto-optical information reproducing apparatus capable of accurately reproducing recorded information even when the recording density is increased. Is to do.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magneto-optical information reproducing apparatus for irradiating a magneto-optical recording medium with a light beam through an objective lens and reproducing recorded information from the reflected light. Magneto-optical of the magneto-optical recording medium contained in
Diffraction by the light generated by the gas effect and the curved surface of the objective lens
The polarization component perpendicular to the polarization direction of the incident light
2 causes to interfere with the same polarization component to the polarization direction of the Shako
A polarizing beam splitter that separates the light into two light beams, and a detection surface that detects each of the separated light beams is divided into at least two parts, and a main dividing line is disposed in a direction parallel to a track of the recording medium. The two multi-segment photodetectors and the multi-segment photodetectors detect the detection signal of the detection surface of each of the multi-segment photodetectors differentially, or differentially detect the sum signal obtained after the addition, and perform Means for generating a reproduction signal by adding or differentially detecting the obtained differential detection signals, thereby achieving a magneto-optical information reproducing apparatus.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a magneto-optical information reproducing apparatus according to the present invention, and shows only a configuration of a reproducing optical system as a main part of the present invention. Therefore, the other configuration is the same as that of the apparatus shown in FIG. 7, and the same parts are omitted in FIG. However, in this embodiment, the objective lens 40 having a curved surface with a large curvature of NA of 0.5 or more is used. In FIG. 1, reference numeral 43 denotes a polarization beam splitter, 45 denotes a half-wave plate, 46 denotes a condenser lens, and 47 denotes a polarization beam splitter as an analyzer, all of which are the same as those in FIG. Also,
Reference numerals 1 and 2 denote four-divided photodetectors in which a detection surface is divided into four. In FIG. 1, the detection surfaces of these four-split photodetectors 1 and 2 are schematically shown, and the directions of the information tracks of the magneto-optical disk 41 are indicated by arrows so that the arrangement relationship with respect to the magneto-optical disk 41 can be understood. I have. 1-1 to 1-4 indicate the respective detection surfaces of the four-split photodetector 1, and arrow D indicates the direction of the information track. Reference numerals 2-1 to 2-4 denote each detection surface of the four-split photodetector 2, and arrow D 'denotes the direction of the information track. The correspondence between the detection surfaces of the four-segment photodetectors 1 and 2 is such that light enters through a polarizing beam splitter 47 as an analyzer.
The left and right positions correspond in reverse. That is, the detection surfaces 1-1 and 2
-1, detection surfaces 1-2 and 2-2, detection surfaces 1-3 and 2-3,
The detection surfaces 1-4 and 2-4 have a corresponding positional relationship.

Reference numerals 3 and 4 denote addition amplifiers for adding detection signals of the detection surfaces of the diagonal positions of the quadrant photodetector 1 respectively, and reference numerals 6 and 7 adjoin each other in the track direction of the quadrant photodetector 1. This is an addition amplifier for adding detection signals of the detection surfaces. Reference numeral 5 denotes a differential amplifier for differentially detecting the sum signal obtained by the addition amplifiers 3 and 4, and reference numeral 8 denotes a differential amplifier for differentially detecting the sum signal obtained by the addition amplifiers 6 and 7. Reference numerals 9 and 10 denote addition amplifiers for adding detection signals of the detection surfaces at the diagonal positions of the quadrant photodetector 2 respectively. Reference numerals 12 and 13 denote detection amplifiers adjacent to the quadrant photodetector 2 in the track direction. This is an addition amplifier for adding the detection signals of the faces. 11 is a summing amplifier 9
And 10 are differential amplifiers for differentially detecting the sum signals obtained by the adders 12 and 13, and 14 are differential amplifiers for differentially detecting the sum signals obtained by the adder amplifiers 12 and 13. Further, reference numeral 15 denotes a differential amplifier for differentially detecting output signals of the differential amplifiers 5 and 11, and a signal obtained by the differential detection becomes a reproduced signal 16 corresponding to pit position recording. 17 is a differential amplifier 8
And an output amplifier for adding the output signals of the pit edge recording to the reproduction signal 18 corresponding to the pit edge recording.

Next, the operation of this embodiment will be described. First,
The light beam emitted from the semiconductor laser 36 is converted into linearly polarized light (P-polarized light) having a polarization direction parallel to the paper surface as in the conventional case. When this light beam enters the objective lens 40, the curvature of the objective lens 40 is large, and the reflectance for polarized light perpendicular to the incident light is significantly different. Therefore, the polarization plane rotates, and only the polarized light perpendicular to the polarization plane of the incident light is observed. Then, as described later, a diffraction image like a four-leaf clover is obtained. The light beams incident on the four-split photodetectors 1 and 2 are light having the same polarization direction as the polarization direction of the P ₊ incident light shown in FIG. 8 and polarization in a direction perpendicular thereto. This includes light of S ₊ and S ₋ generated by the Kerr effect and Faraday effect of the magneto-optical disk 41 and light generated by the curved surface of the objective lens 40 as described above.

FIG. 2A is a diagram showing P ₊ light in the distribution of light immediately before entering the polarizing beam splitter 47 as an analyzer, and FIG. 2B is a diagram showing A− in FIG. FIG. 4 is a diagram illustrating the amplitude of P ₊ light in a cross section taken along line A ′. Note that the four squares shown in FIG. 2A are detection surfaces of the four-segmented photodetector, and P ₊ light is projected on the detection surface. FIG.
In (a), the light of P ₊ is indicated by oblique lines, is evenly distributed on the four detection surfaces, and the phases of the light are almost the same on the four detection surfaces. The amplitude of light in the cross section taken along the line AA 'is shown in FIG.
(B). FIG. 3A is a diagram showing S-polarized light generated on the curved surface of the objective lens 40 in the distribution of light immediately before being incident on the polarization beam splitter 47 as an analyzer. It is to be noted that the projection is similarly shown projected on the detection surface of the quadrant photodetector. As is clear from FIG.
The light distribution is shaped like a four-leaf clover, and the light of each leaf projects onto four detection surfaces. The lights of leaves at diagonal positions have the same phase, and the phase difference between lights of adjacent leaves is π. FIG.
2A and the light shown in FIG. 2A have the same phase. FIGS. 3 (b) and 3 (c) show BB in FIG. 3 (a).
This is a diagram showing the amplitude of the light in the cross section taken along the line 'C' and the line CC '. The amplitude is as shown in the figure from the phase relationship between the four leaves described above. The light shown in FIG. 2 and FIG.
Regardless of the upper magnetization direction, the distribution is constant. In the present invention, these two lights and the S ₊ and S ₋ lights that change in the state of magnetization on the magneto-optical recording medium are separated by a polarization beam splitter 47 as an analyzer, and are separated by two quadrant photodetectors. Information is reproduced by detecting a change in the light quantity distribution resulting from the interference of the three lights.

The information reproduction will be further described with reference to FIG. FIG. 4A is a diagram showing recorded magnetic domains and a light spot for reproduction. Reference numeral 19 denotes an information track, and reference numeral 20 denotes a domain on the track. In the present embodiment, a magnetic field modulation method is adopted, and therefore, the domain 20 has an arrow blade shape.
Of course, an optical modulation method may be used. In addition, the magnetization of the magneto-optical disk 41 is all initialized downward at the time of initialization, and therefore the magnetization of the domain 20 is upward. Light spots 21, 23, 2 on information track 19
Scan as shown as 4,25. Arrows D and D 'shown in the figure correspond to D and D' shown in FIG. FIG.
(B) shows the position of each light spot in FIG. (A), and the polarization beam splitter 4 of the S-polarized light generated by the magneto-optical effect.
FIG. 7 is a diagram illustrating a distribution immediately before the light is incident on a light-receiving element; Note that, also here, the projection is shown on the detection surface of the quadrant photodetector.
At the positions of the light spots 21 and 25, since the inside of the light spot is all downward magnetization, light diffraction does not occur, and
As shown as 0, the distribution is circular. The phase of the light at this time is the same as the phase of the light shown in FIG. 2A and the phase of the light indicated by E in FIG. That is, assuming that the light shown in FIG. 2 is the P ₊ light shown in FIG. 8, the distribution of the light shown by 26 and 30 is the S ₊ light.

At the positions of the light spots 22 and 24, since the boundary between the upward magnetization and the downward magnetization, that is, the edge of the domain 20 is located in the light spot, the information tracks 19 are located.
The light is diffracted in a direction parallel to the direction, and the light distribution is divided into right and left as indicated by 27 and 29. Although the phase difference between the left and right lights is π, the phases of the left and right lights are reversed at 27 and 29. In 27 and 29, the left and right lights are 27a, 27b and 29a.
And 29b, the light indicated by 27a and 29b is S ₊ , the light indicated by 27b and 29a is S ₋ light, and when the edge of the domain 20 is located in the light spot,
Distribution of light S ₊ and S _- becomes the light are mixed. Further, at the position of the light spot 23, since the inside of the light spot has substantially upward magnetization, there is almost no diffraction of light, and
As shown by a circle, the distribution becomes substantially circular. The light at this time is S ₋ light having a phase difference of π compared to 26 and 30. FIG. 4C is a diagram showing the amplitude of light in the cross section taken along line AA ′ in FIG. 4B at each position of the light spot, and changes as shown in the figure according to the position of the light spot.

FIGS. 4D and 4E show S-polarized light generated on the curved surface of the objective lens 40 shown in FIG. 3 and FIG.
The light distribution resulting from the interference of the S-polarized light generated by the magneto-optical effect shown in FIG.
It is a figure expressed as the amplitude of light in the section of line C '. FIG. 4D shows the amplitude of light on the line BB ′,
(E) is the amplitude of light on the line CC ′. FIGS. 4F and 4G show S-polarized light generated by the curved surface of the objective lens 40, S-polarized light generated by the magneto-optical effect, on the separation surface of the polarizing beam splitter 47 as an analyzer. FIG. 3 is a diagram showing the difference in the amount of light detected on each detection surface when the P ₊ light shown in FIG. 2 is split into two parts, and these are detected by the four-divided photodetectors 1 and 2, respectively. FIG. 4F shows the detection surface of the four-segment photodetector 1, and FIG.
This is the difference in the detected light amount on the detection surface of the split photodetector 2. FIG.
In (f) and (g), large and small, large and small, small and large,
Indicated as small and small. As described with reference to FIG. 1, since the light incident on the four-split photodetector 2 is reflected by the polarization beam splitter 47, the correspondence of the detection surface to the detection surface of the four-split photodetector 1 is reversed. For example, FIG.
4 (g) at the position of the light spot 21 shown at the left end.
Looking at the distribution of light on the split photodetector, the detection surface 1-1 of the quadrant photodetector 1 and the detection surface 2- of the quadrant photodetector 2
1 corresponds. The light incident on these detection surfaces is shown in FIG.
The large upward amplitude (S ₊ direction component shown in FIG. 8) on the left side indicated by F of the light amplitude in the cross section taken along the line BB ′ shown in (d) and the upward amplitude shown in FIG. P shown in
₊ Direction component), and is light that has rotated to the + θ side. As for the arrangement of the polarization beam splitter 47, the one that functions as an analyzer at +45 degrees enters the four-split photodetector 1 shown in FIG. ), The light amount incident on the detection surface 1-1 is larger than the light amount incident on the detection surface 2-1. Large and large are shown as large and small on the detection surface 2-1 (large and large> large and small).

The detection surface 1-2 corresponds to the detection surface 2-2, and the light incident on these detection surfaces is represented by G, which is the amplitude of the light in the cross section taken along the line BB 'shown in FIG. The small downward amplitude on the right side shown (the S _- direction component shown in FIG. 8) and FIG.
The light having the upward amplitude (P ₊ direction component shown in FIG. 8) indicated by is combined and rotated to the −θ side. In this case, the amount of light incident on the detection surface 1-2 is smaller than the amount of light incident on the detection surface 2-2, which is shown as small and small on the detection surface 1-2 and small and large on the detection surface 2-2. (Small <small). The detection surface 1-3 corresponds to the detection surface 2-3.
This is light in which the small downward amplitude indicated by H of the light amplitude in the cross section taken along the line CC ′ shown in (e) and the upward amplitude light similarly shown in FIG. 2 are combined. The amount of light on the detection surface 1-3 is larger than the amount of light on the detection surface 2-3, which is shown as large and large on the detection surface 1-3 and large and small on the detection surface 2-3. Further, on the detection surfaces 1-4 and 2-4, C in FIG.
2 is light obtained by combining the large upward amplitude indicated by I of the light amplitude in the cross section along the line C ′ and the upward amplitude light in FIG. 2. In this case, the light amount on the detection surface 1-4 is smaller than the light amount on the detection surface 2-4, which is shown as small and small on the detection surface 1-4 and small and large on the detection surface 2-4. Similarly, at each position of the light spots 22 to 25, the four-divided photodetector 1
4 and FIG. 4 show the amounts of light on the detection surfaces, respectively.
The results are as shown in (f) and (g).

The detection signals from the respective detection surfaces of the four-split photodetectors 1 and 2 are output to an analog arithmetic circuit composed of an addition amplifier and a differential amplifier as described with reference to FIG. The detection signals of the detection surfaces 1-1 and 1-3 and the detection signals of the detection surfaces 1-2 and 1-4 at the diagonal positions of the four-split photodetector 1 are added by the addition amplifiers 3 and 4, respectively. The sum signal is differentially detected by the differential amplifier 5. The detection signals of the detection surfaces 1-1 and 1-2 and the detection surfaces 1-3 and 1-4 of the competitors adjacent to each other in the track direction are added by addition amplifiers 6 and 7, respectively. The differential detection is performed by the dynamic amplifier 8. on the other hand,
Detection surfaces 2-1 and 2- at the diagonal positions of the quadrant photodetector 2
3 and the detection signals of the detection surfaces 2-2 and 2-4 are added by addition amplifiers 9 and 10, respectively, and the sum signal is differentially detected by the differential amplifier 11. In addition, detection surfaces 2-1 and 2-2 and detection surfaces 2-3 and 2-4 of competitors adjacent to each other in the track direction are provided.
Are added by the addition amplifiers 12 and 13, respectively, and the sum signal is differentially detected by the differential amplifier 14.

The output signals of the differential amplifier 5 and the differential amplifier 11 are further differentially detected by the differential amplifier 15 to generate a reproduction signal 16 as shown in FIG. The obtained reproduced signal has a negative constant level in the downward magnetization region, a positive constant level in the upward magnetization region, and a negative constant level in the mixed region of the upward magnetization and the downward magnetization where the edge of the domain 20 is located in the light spot. From positive to negative or from positive to negative. That is, the rising edge corresponding to both ends of the domain 20,
Alternatively, it becomes a falling pulse-like signal, and becomes a reproduced signal of the information of the pit position recording that gives the meaning of the information to the center position of the domain. On the other hand, the output signals of the differential amplifiers 8 and 14 are further added by an addition amplifier 17 to generate a reproduced signal 18 as shown in FIG. This reproduced signal is a reproduced signal having a 0 level in the region of downward magnetization and an upward magnetization, and a positive or negative peak at the edge of the domain 20. By detecting this peak position, the edge of the domain can be detected, and the information recorded by pit edge recording can be reproduced. It should be noted that when performing analog arithmetic, by changing the combination of detection surfaces,
The polarity of the reproduced signal shown in (h) and (i) can be inverted.

In the above embodiment, the signal reproduction which can be used for both the pit position recording and the pit edge recording has been described. However, when the recording medium is mounted on the apparatus, the pit position recording is automatically performed according to the recording medium. It is desirable to switch between reproduction of pits and pit edge recording. Therefore, an example of the switching control device will be described. First, as shown in FIG. 5, a mark 33 indicating whether the disk is a pit position recording disk or a pit edge recording disk is added to the case 32 of the magneto-optical disk 41. Mark 3
Numeral 3 is for optically detecting, for example, a pit position recording disk has a high reflectance mark, and a pit edge recording disk has a low reflectance mark. On the other hand, a light emitting diode 34 and an optical sensor 35 are provided on the apparatus side, and when the disc is mounted on the apparatus, the mark 3
3 and the reflected light is received by the optical sensor 35. Therefore, when the magneto-optical disk is mounted on the apparatus, the signal reproduction may be switched by the procedure shown in FIG. That is, the magneto-optical disk is mounted on the device (step 1), the mark 33 of the disk case 32 is checked based on the detection signal of the optical sensor 35 (step 2), and the result is used to determine whether the disk is a bit position recording disk or not. Discrimination whether the disc is for edge recording (step 3),
The reproduction selection corresponding to the pit position recording based on the determination result (step 4) or the reproduction selection corresponding to the pit edge recording (step 5) may be performed. As described above, when the magneto-optical disk is mounted on the apparatus, it is possible to automatically select the signal reproduction corresponding to the disk recording method.

In the above embodiment, the signal reproduction for both the pit position recording and the pit edge recording can be performed. However, either one of the dedicated reproducing apparatus may be used. In particular, in the case of a dedicated reproducing apparatus for pit edge recording, detection surfaces adjacent to each other in the track direction of each four-divided photodetector may be integrated. That is, pit edge recording is performed by substituting a two-segment photodetector having a dividing line in the track direction, adding detection signals of the detection surfaces of the respective two-segment photodetectors, and differentially detecting the obtained sum signal. Can be obtained. Further, it is also possible to perform the above-described signal reproduction using a multi-segment photodetector other than the four-segment or two-segment photodetectors.

[0023]

According to the present invention as described above, according to the present invention, the serial
Recorded information even if the recording pit size is smaller than the light spot
Signal can be detected accurately, and signal
Can be done accurately. Especially for pit edge recording
Shift phenomena due to deterioration of transfer characteristics of optical head
And correct the recorded information even in pit edge recording.
It can be reproduced exactly .

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of a magneto-optical information reproducing apparatus according to the present invention.

FIG. 2 shows a P just before entering a polarizing beam splitter 47;
FIG. 3 is a diagram showing a distribution of ₊ light projected on a detection surface of a four-divided photodetector, and a diagram showing an amplitude of light in a cross section taken along line AA ′ of the detection surface.

FIG. 3 is a diagram showing a distribution of S-polarized light generated on a curved surface of an objective lens immediately before entering a polarizing beam splitter 47 onto a detection surface of a four-segment photodetector, and FIG. It is the figure which showed the amplitude of the light in the cross section of B 'line and CC' line.

FIG. 4 is a diagram for explaining an information reproducing operation of the embodiment of FIG. 1;

FIG. 5 is a diagram showing a mark for discriminating a recording method added to a case of a magneto-optical disk and a sensor for detecting the mark.

FIG. 6 is a flowchart showing a procedure for switching control of signal reproduction corresponding to a pit position recording disk and a pit edge recording disk.

FIG. 7 is a configuration diagram showing an optical system of a conventional magneto-optical information recording / reproducing apparatus.

FIG. 8 is a diagram illustrating a polarization direction of linearly polarized light incident on a magneto-optical recording medium, a rotation state corresponding to a magnetization direction of reflected light on the medium, and a change state of the rotation state with respect to an analyzer.

FIG. 9 is a diagram showing each pit row of pit position recording and pit edge recording and detection signals thereof.

[Explanation of symbols]

1, 4 split photodetector 3, 4, 6, 7, 9, 10, 12, 13, 17 summing amplifier 5, 8, 11, 14, 15 differential amplifier 19 information track 20 domain 21 to 25 light spot 36 Semiconductor laser 40 objective lens 41 magneto-optical disk 47 polarization beam splitter

Claims (4)

(57) [Claims] 1. A magneto-optical information reproducing apparatus for irradiating a magneto-optical recording medium with a light beam through an objective lens and reproducing recorded information from the reflected light , the light of the magneto-optical recording medium being included in the reflected light. Magnetic effect
Diffracted by the light generated by the
Flip was incident light of the light with the polarization direction perpendicular to the polarization component of the incident light
A polarization beam splitter that interferes with the same polarization component as the polarization direction and separates the two light beams, and detects each of the separated light beams. The detection surface is divided into at least two, and the main dividing line is Two multi-segment photodetectors arranged in a direction parallel to a track of a recording medium; and differential detection of a detection signal of a detection surface of each of the multi-segment photodetectors;
Or means for differentially detecting the sum signal obtained after the addition and adding or differentially detecting the differential detection signal obtained from each multi-segment photodetector to generate a reproduced signal. Characteristic magneto-optical information reproducing apparatus. 2. The multi-segment photodetector includes:
And a quadrant photodetector divided in the direction
And the reproduction signal generation means is provided at a diagonal of the quadrant photodetector.
The detection signals of the position detection planes are added, and the obtained additions are added.
Differential detection of signal and obtained by each multi-segment photodetector
By detecting the differential detection signal differentially, the pit position can be recorded.
2. The magneto-optical information reproducing apparatus according to claim 1 , wherein a reproducing signal corresponding to the recording information is generated . 3. The multi-divided photodetector is arranged in a track direction.
And a quadrant photodetector divided in the direction
The reproduction signal generating means operates the four-split photodetector.
Detection signals from adjacent detection surfaces in the
And each of the obtained sum signals is differentially detected, and
By adding the differential detection signals obtained by the photodetector,
Generates a playback signal corresponding to the information of the pit edge recording
2. The magneto-optical information reproducing apparatus according to claim 1 , wherein: 4. A reproduction signal generating means, comprising : a magneto-optical recording medium.
Detects media identification information added to the body and
This is a recording medium for recording pits or recording for recording pit positions.
4. The magneto-optical information reproducing apparatus according to claim 2, further comprising means for determining whether the medium is a medium .