JP3369385B2 - Magneto-optical recording / 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 recording / reproducing apparatus for recording a signal on a magneto-optical disk such as a magneto-optical disk device or an MD (mini disk) player.

[0002]

2. Description of the Related Art A magneto-optical recording / reproducing apparatus uses a semiconductor laser element to record information signals at high density on a magneto-optical recording medium, for example, a magneto-optical disk (hereinafter referred to as a disk), or to record information signals. It is used to reproduce recorded information signals, and is widely used as an auxiliary storage device of an information processing device such as a computer and a recordable / reproducible music medium.

In the magneto-optical recording / reproducing apparatus as described above, the general structure and operation of an optical pickup for recording / reproducing will be described. First, a light beam emitted from a semiconductor laser is converted into a parallel light flux by a collimator lens. It is focused on the disc by the objective lens to form a spot. To realize high-density information recording,
The light beam is focused and the diameter is 1 μm on the disc.
It is necessary to form minute spots.

The reflected light beam is returned to a parallel light beam by the objective lens, reflected by the polarization beam splitter, polarized and separated by the Wollaston prism, and irradiated onto the light receiving element by the condenser lens. It

The light receiving element detects the information signal recorded on the disk from the irradiated light beam and simultaneously detects the servo signal. Using this servo signal, the objective lens is two-dimensionally driven so that the spot of the light beam is always focused on a desired position on the disk.

In the polarization beam splitter, a part of the light beam from the collimating lens is reflected and the light output monitor irradiates the light beam to control the output of the light beam. The output of the light beam is monitored by the output of the light output monitor.

On the other hand, although the information signal is recorded in the direction of magnetization on the above-mentioned disk, when the information signal is recorded, the magneto-optical film in the disk is heated to the Curie temperature or higher and the magnetic field applied is changed. This is performed by changing the direction and forming a magnetized region (hereinafter referred to as a pit). This is because the magneto-optical film has the property that, in an environment above the Curie temperature, the magnetization direction changes due to the influence of the direction of the surrounding magnetic field. The inside is set to the Curie temperature or lower, but the output of the light beam is increased during recording, and the direction of magnetization is determined by applying a magnetic field to the magneto-optical film above the Curie temperature in the spot. Then, if the direction of the magnetic field is maintained until the temperature becomes equal to or lower than the Curie temperature, pits whose magnetization direction is fixed according to the information signal to be recorded are formed.

As described above, the magneto-optical recording medium can stably hold an information signal in normal use,
It is also a recording medium in which the information signal can be rewritten if necessary.

[0009]

In the above, during reproduction, the light beam reflected from the magneto-optical film other than the pits within the spot diameter will also be received by the light receiving element. If the proportion of the reflected light beam increases, the S / N ratio of the reproduced information signal deteriorates, so it can be said that the spot diameter should be close to the size of the pit width.

However, as shown in FIG. 14A, the light intensity distribution of the spot focused on the disk is usually a distribution similar to the Gaussian distribution, and becomes larger as it gets closer to the center of the spot. Therefore, the temperature of the magneto-optical film located near the center of the spot becomes higher than that of the magneto-optical film located near the periphery of the spot (FIG. 14B). Further, when recording a signal, the direction of magnetization can be changed only in the region of the Curie temperature Tc or higher, so that the magneto-optical film side located near the center of the spot contributes to signal recording. Therefore, as shown in FIG. 15, in the magneto-optical film, a region having a Curie temperature or higher, and a pit width W _M
Is usually smaller than the spot diameter W _L.

Therefore, in the spot light intensity distribution as described above, in order to increase the width W _M of the pit, if the output of the semiconductor laser is increased to reach the Curie temperature Tc or more up to the vicinity of the peripheral portion, the spot is increased. There is a possibility that the temperature of the central portion becomes too high and the melting temperature of the magneto-optical film is exceeded to damage the magneto-optical film.

On the other hand, since the spot diameter W _L does not change even if the output of the light beam is changed, the light beam reflected by the disc during reproduction contains all information within the spot diameter W _L. However, since the width W _M of the pit in the pit recorded as described above is smaller than the spot diameter W _L during reproduction,
The light beam has a low rate of being reflected by the pit,
The S / N ratio of the reproduction signal decreases.

As a result, in general, the magneto-optical recording medium is inferior in characteristics such as jitter and error rate as compared with the pre-mastered type optical recording medium in which signals are recorded by the unevenness of the pits. Therefore, it was necessary to improve the reading accuracy, which was a factor of reducing the yield in manufacturing the device.

In order to avoid the above problem, the width of the recorded pits should be increased. For example, if the output of the semiconductor laser during recording is increased, as shown in FIG. 16, the spot diameter W _L does not change, but the Curie temperature Tc
Since the above-mentioned area is expanded, the width W _M of the pit can be increased. However, since the light intensity distribution in the spot is a Gaussian distribution, it is impossible to raise the temperature of the entire spot to the Curie temperature or more. Further, if the light output is raised too much, as described above, the recording layer is formed in the center of the spot. It can be damaged.

The present invention has been made to solve the above problems, and an object thereof is to increase the width of a pit with respect to the spot diameter at the time of reproduction without damaging the magneto-optical film at the time of recording. An object of the present invention is to provide a magneto-optical recording / reproducing device capable of improving signal reproduction characteristics.

[0016]

[0017]

In order to solve the above-mentioned problems, a magneto-optical recording / reproducing apparatus according to the invention of claim 1 uses an objective lens to direct a light beam emitted from a light source onto a recording medium. In a magneto-optical recording / reproducing apparatus that records and reproduces an information signal on a recording medium by converging light, the spot diameter of the spot irradiated on the recording medium is adjusted so that the spot diameter during recording becomes larger than the spot diameter during reproduction. A spot diameter varying means for changing the size is provided, and the spot diameter varying means is
Change the defocus distance between the recording medium and the objective lens.
The objective lens driving means is provided to output the light beam.
A light beam output control means for controlling is provided.
Light emitted from the light source during recording by the optical output control means
The beam power is controlled according to the actual defocus distance.
It is characterized in that that. With the above configuration, the spot diameter during recording can be made larger than the spot diameter during reproduction.

[0018]

In the above arrangement , when the distance between the recording medium and the objective lens is changed, the defocused state is established and the spot diameter can be changed. In this case, at the time of recording according to the actual defocus distances, do it by changing the output of the light beam, the recording medium can be always formed the magnetization regions with a stable width. When the light intensity distribution of the light beam incident on the objective lens is made different as in claim 2 , the spot diameter at the time of recording and at the time of reproducing can be changed while the distance between the recording medium and the objective lens remains unchanged. .

Particularly when a light source whose wavelength changes with an increase in output, such as a semiconductor laser, is used, a filter for selectively transmitting a specific wavelength is used as in claim 2 , and the light in the optical path is changed. By changing the intensity distribution,
The spot diameter during recording and playback can be changed. Specifically, as in claim 3 , the filter has a characteristic of selectively transmitting the wavelength at the time of reproduction, and when the peripheral portion of the optical path is provided so as to be shielded in an annular shape, a diaphragm is provided at the time of recording. It becomes a state, and like Claim 4 ,
If the filter has the property of selectively transmitting the wavelength at the time of recording, and if it is provided so as to shield the central part of the optical path in a disk shape, it will give super resolution, and the spot diameter at the time of recording will be It can be larger than the spot diameter. With any of the above-mentioned configurations, it is possible to make the spot diameter during recording larger than the spot diameter during reproduction.

Further, the reference optical magnetic recording and reproducing apparatus according to the invention of claim 5, in order to solve the above problems, for outputting the light beam output control means for controlling the output of the upper climate beam, the reference signal A signal generation means and a comparison means for comparing the reproduction signal and the reference signal are provided, and before the information signal is recorded, the defocus distance between the recording medium and the objective lens is set to the recording medium. Along with multiple settings, the reference signal is recorded / reproduced by combining it with multiple light beam outputs, and the original reference signal is compared with the reproduced reference signal to obtain the best reproduction signal. It is characterized in that the information signal is recorded by the combination of the light beam output and the light beam output. With the above configuration, even if the optimum recording condition changes due to variations in temperature or composition of the recording medium, in the recording environment, the best reproduction signal can be obtained from a plurality of recording conditions in advance. Since the condition is selected, it is always possible to record a high quality information signal.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. In each of the following embodiments, the spot diameter at the time of recording is made larger than the spot diameter at the time of reproducing, By forming a pit having a width wider than that formed with the same spot diameter at the time of reproduction, the area of the pit occupied in the spot at the time of reproduction is increased, and the S / N ratio of the reproduction signal is increased. The purpose is to improve.

[First Embodiment] The following will describe one embodiment of a magneto-optical recording / reproducing apparatus according to the present invention with reference to FIGS. 1 to 6.

As a configuration of an optical system in the magneto-optical recording / reproducing apparatus in the present embodiment, as shown in FIG. 2, a semiconductor laser 2, a collimating lens 3, a polarization beam splitter 4, an objective lens 5 and an objective lens drive. Mechanism 6 and
The Wollaston prism 7, the condenser lens 8, the light receiving element 9, the light output monitor 10, and the detection signal from the light receiving element 9 are received, and the objective lens driving mechanism 6 (spot diameter changing means / objective lens driving means) is received. A focus servo circuit 11 (spot diameter varying means / objective lens driving means) for controlling the drive of the lens and a tracking servo circuit 12 are provided. Then, the light beam 1 emitted from the semiconductor laser 2 becomes a parallel light flux by the collimator lens 3, passes through the polarization beam splitter 4, and is then focused by the objective lens 5 on the disk 13 (recording medium). The output of the light beam 1 which forms a spot and is reflected by the polarization beam splitter 4 is detected by an optical output monitor 10 in order to control its output.

On the other hand, the light beam 1 reflected by the disk 13 passes through the objective lens 5, is reflected by the polarization beam splitter 4, is polarized and separated by the Wollaston prism 7, and then is read by the light receiving element 9. The signal is detected. The light receiving element 9 detects the information signal recorded on the disk 13 and simultaneously detects the servo signal. That is, the detected servo signal is focused by the focus servo circuit 11 so that the spot of the light beam 1 is always focused on a desired position on the disk 13.
And to the tracking servo circuit 12. The servo signals are a focus servo signal (Focus Error Signal: hereinafter abbreviated as FES) corresponding to the defocus amount of the spot, and a tracking servo signal (Tracking Error Signal: hereafter TE) corresponding to the amount of deviation from the track.
(Abbreviated as S)).

The objective lens 5 is supported by a leaf spring, a wire or the like, and is driven by an objective lens driving mechanism 6 composed of a coil and a magnetic circuit in a direction perpendicular to the surface of the disk 13 (the focal point is defocused) based on the servo signal. Direction) or in a direction parallel to the surface of the disk 13 and orthogonal to the track (shift direction from the track).
The servo signal detection system is omitted in FIG.

In the optical system as described above, the focus servo is normally adjusted so that the jitter value at the time of disk reproduction becomes the best, but in this embodiment, a typical FES detection method is not used. The point aberration method is used. In the astigmatic method, as shown in FIG. 3, the light receiving element 9 are divided into four, the information signals obtained from the respective light receiving elements 9a~9d I _a ~I _d (current value) ,
The output (V _a + V _d ) obtained by inputting (I _a + I _d ) into the current-voltage conversion circuit 20 and the output (V obtained by inputting (I _b + I _c ) into the current-voltage conversion circuit 21. _b +
V _c) and the subtracted value _{(V a + V d) -} (V b + V c)
Is usually FES. Since the light receiving elements 9a to 9d generate a current proportional to the irradiation area of the spot,
As shown in (a), since the circular spot is located at the center of the four-divided light receiving element 9 when the focus is achieved, the light receiving elements 9a to 9d have the same spot irradiation area. As a result, the values of the obtained signals I _{a to} I _d become equal, so the value of the FES becomes 0 from the above calculation.

On the other hand, if the focal length of the objective lens 5 with respect to the disc does not match, the spot on the light receiving element 9 will be elliptical. For example, when the position of the objective lens 5 is too far from the disc, the elliptical shape shown in FIG. 4B is obtained, and FES <0.
The elliptical shape shown in (c) is obtained, and FES> 0. FE
Since the absolute value of S increases as the deviation from the focal length increases, it can be considered that the value of FES indicates the amount of deviation of the focus. That is, if the position of the objective lens 5 is controlled so that FES = 0, the focal length of the objective lens 5 can be maintained at a predetermined position.

In the above, when the focus is achieved (hereinafter,
It is said that the FES will be 0 during focusing), but due to variations in the quality of each member that makes up the optical system, etc.
However, there are some spots on the disk 13 that are not accurately focused, and it is necessary to adjust the optical system so that the FES becomes 0 when focusing. However, since the above adjustment cannot completely eliminate the variation, the variation of the optical system actually remains. Therefore,
The balance adjustment circuit 22 provided in the focus servo circuit 11 performs fine adjustment to correct the variation remaining in the adjustment of the optical system.

For example, after the output (V _b + V _c ) side is subjected to gain adjustment (× k times) by the balance adjustment circuit 22, the subtraction circuit 23 subtracts it from (V _a + V _d ). The gain value k may be selected so that (V _a + V _d ) −k × (V _b + V _c ) becomes 0 as FES at the time of focusing. The balance adjustment circuit 22 is composed of a variable resistor, an electronic potentiometer, or the like. The above adjustment is usually called focus gain balance adjustment, focus offset adjustment, or the like. Then, in the above, if the gains at the time of recording and at the time of reproducing are changed, the focus offset amount (focal shift distance) changes, and the spot diameter on the disk 13 formed by the objective lens 5 during recording and reproducing. And will change.

As a specific example, as shown in FIG. 5, the circuit configuration is such that the gain of the balance adjusting circuit 22 is adjusted by the electronic volume, and the electronic volume is controlled by the microcomputer 24 according to the switching of the recording / reproducing mode. You can control it.

A method of increasing the width of the pit formed on the disk by defocusing the spot as described above will be described below with reference to FIG. In FIG. 1, the graph shows the temperature distribution of the magneto-optical film by the spots at the time of reproduction. In the case of the spots at the time of normal recording, as shown in the graph, the pit width is the same as the spot diameter W _L at the time of reproduction W _M has been obtained.

When the light beam is defocused from the state of the above graph, the temperature distribution shown in the graph is obtained. In this case, the spot diameter increases to W _L ′, but the light intensity in the central portion of the spot decreases and the pit width decreases to W _M ″, so that the information signal should be recorded sufficiently. So, as shown in the graph, in the defocused state,
That is, if the output of the semiconductor laser 2 is increased while the spot diameter is W _L ′, the pit width W _M ′ can be obtained without raising the peak temperature of the central portion more than necessary. In FIG. 1, the spot diameter W _L at the time of reproduction and the pit width W _M ′ are set to be equal.

[0034] Consequently, with respect to the spot diameter W _L at the time of reproduction, the width W of the width W _M of pits formed during recording pit
_Since it becomes _M ' , and the width of the pit becomes relatively large, the S / N ratio of the reproduced signal can be improved. However,
When increasing the spot diameter by defocusing, the larger the focus offset amount is, the lower the TES sensitivity becomes, and thus the tracking servo gain also decreases, and the tracking becomes unstable. Therefore, if the tracking servo gain adjusting circuit 25 is provided as shown in FIG. 5 and control is performed by using the microcomputer 24 so as to increase the gain of the tracking servo circuit 12 according to the focus offset amount, stable tracking can be achieved. Can be secured.

The width of the recorded pit depends on the output of the semiconductor laser 2 and the focus offset amount. Therefore, even if surface wobbling occurs when the disk 13 rotates, the pit width changes, so it is necessary to control the focus offset amount. However, the tracking accuracy depends on the surface wobbling amount of the disk 13 and the gain of the servo system. Depends on
For example, if the gain of the servo system is 60 dB (1000 times) and the displacement of the recording surface due to surface runout is 0.1 mm, the servo tracking accuracy at this time is 0.1 mm ÷ 1000 = 0.1 μm
Similarly, if the displacement is 0.2 mm, the servo tracking accuracy is 0.2 μm, and the focus offset amount changes by the servo tracking residual amount according to the displacement of the disk 13 due to the surface wobbling. That is, even if the objective lens 5 is made to follow the displacement of the disc 13 by the focus servo circuit 11, the state of the focus offset actually changes due to the displacement of the recording surface of the disc 13. . A shift amount with respect to a predetermined focus offset amount is called a residual error signal. As previously mentioned,
Since the width of the recorded pit depends on the focus offset amount, if the relative focus offset amount with respect to the disk 13 changes due to the residual error signal, the pit width also changes.

In order to perform more stable signal recording in response to the above case, the output of the semiconductor laser 2 during recording is controlled according to the residual error signal. For example,
As shown in FIG. 6, if the actual FES value and the predetermined FES value are monitored by the comparator 26 and it is detected that the FES value deviates from the predetermined value, the microcomputer 24 will
Semiconductor laser 2 for (Auto Power Control) circuit 27
Adjust the output of. For example, if the value of FES becomes smaller than the predetermined value, it means that the spot diameter becomes larger than the predetermined spot diameter, and the relative focus offset amount increases. If the value of FES becomes larger than a predetermined value while making it smaller to narrow the width of the recorded pit,
Since the spot diameter is smaller than the predetermined spot diameter and the relative focus offset amount is decreasing, the output of the semiconductor laser 2 is increased and the width of the recorded pit is controlled to be wide. . In this way, it is possible to control so that the width of the recorded pits does not change even if a residual error occurs due to the surface contact of the disk 13 during recording.

On the other hand, the width of the pit formed by the spot during recording also depends on the recording sensitivity of the magneto-optical film used for the disk 13, and the recording sensitivity of the magneto-optical film is
It changes due to variations in Curie temperature due to variations in composition, variations in reflectance on the surface of the magneto-optical film, and the like. For example, if the Curie temperature of the composition that constitutes the magneto-optical film is low, for a light beam of the same output, the region above the Curie temperature is wider, and if the reflectance of the surface is low,
Since the light energy is absorbed more and the overall temperature distribution rises, the area above the Curie temperature also widens, and a wider pit is formed in each case. If the width is too wide, it may affect signal reading and adjacent pits, so in order to perform stable signal recording, the spot size (output, output, Spot diameter)
Etc. need to be set.

Therefore, the optical pickup 1 of the present embodiment
Although not shown in the figure, a signal generating circuit (reference signal generating means) for generating a dummy reference signal and a comparator (comparing means) for comparing the reproduced signal and the reference signal are provided, and Before recording,
Trial writing was performed on the disc by combining various focus offset amounts and the output of the light beam, and the obtained reproduction signal and the above reference signal were compared, and a predetermined pit width at which the reproduction signal had the best quality was obtained. Therefore, the combination of the focus offset amount and the light beam output is selected. As a result, stable information signal recording can be performed without depending on the external environment or the composition of the magneto-optical film of the disc.

[0039] In the above, by controlling the the time of recording and the focus offset and the semiconductor laser 2 outputs the reproduction, had changed the size of the spot diameter, the recording
An optical head for reproduction and an optical head for reproduction may be separately provided, and an optical head drive means (numerical aperture switching means) may be provided so that the optical heads are exchanged during recording and reproduction. The spot diameter is the objective lens 5 of the laser wavelength λ.
Is proportional to λ / NA, so in the above case, the numerical aperture of the objective lens of the recording optical head is smaller than that of the objective lens of the reproducing optical head. If selected, the spot diameter during recording can be made larger than the spot diameter during reproduction.

In this case, two systems of optical heads are required, but since it is not necessary to control the output of the semiconductor laser 2 and the focus offset amount, the tracking servo gain does not decrease. Of course, only the objective lens is 2
A system may be prepared and switched.

[Second Embodiment] The following will describe another embodiment of the present invention in reference to FIGS. 7 to 13. For convenience of explanation, a configuration having the same function as the configuration shown in the drawing of the first embodiment is
The same reference numerals are given and the description thereof is omitted.

In the first embodiment, the output of the semiconductor laser 2 and the focus offset amount are adjusted so that the spot diameter irradiated on the disc is different between recording and reproducing, so that the pit width during recording is increased. Was made relatively large to improve the S / N ratio of the reproduction signal, but the spot diameter condensed by the objective lens 5 is λ / N as described above.
It depends not only on A but also on the light intensity distribution of the light beam incident on the objective lens 5.

For example, a case where a light beam having a flat intensity distribution is incident on the objective lens 5 and condensed, and a case where the semiconductor laser 2 is used.
In comparison with the case where a light beam having a distribution similar to a Gaussian distribution in which the light intensity of the central portion is higher than that of the peripheral portion is incident on the objective lens 5 and is condensed, the latter is condensed. The spot diameter becomes larger. This is because in the latter case, since the light is strong in the central part of the light flux and weakens toward the peripheral part, the peripheral part of the aperture of the objective lens is not used as compared with the central part, and the aperture is substantially opened. This is because it can be considered that light is condensed by a small number of objective lenses. On the contrary, in the case of a light flux whose light intensity at the central portion is weaker than that of the peripheral portion, a so-called super-resolution is obtained in which the spot diameter is smaller than that of a light flux having a flat light intensity distribution. Utilizing the above, in the present embodiment, the spot diameter is changed by making the light intensity distribution of the light beam incident on the objective lens 5 different during recording and during reproduction.

For example, according to the standard called MD (Mini Disc), the output of the light beam at the time of recording is 7 to 8 times as high as the output at the time of reproducing, but the semiconductor laser generally increases with the increase of the output. It has the property of increasing the wavelength. That is, the wavelength α during recording is longer than the wavelength during recording (probably α) and the wavelength during reproduction (probably β).

Therefore, as shown in FIG. 7, the objective lens 5
An interference filter 31 (light intensity distribution switching means) is arranged on the semiconductor laser 2 side. This interference filter 31
Is formed into a thin plate donut shape shown in FIG. 8, and has a maximum transmittance at the reproducing wavelength β as shown in FIG. 9 with respect to the recording wavelength α and the reproducing wavelength β. The wavelength α has a characteristic that it is difficult for the wavelength α to pass through the interference filter 31. Therefore, at the time of reproduction, FIG.
As shown in FIG. 10, the light beam passes through the entire surface of the objective lens 5 to form a spot, but at the time of recording, the light beam does not pass through the interference filter 31 portion as shown in FIG. Since the light beam only passes through the central portion of the objective lens 5 corresponding to the region corresponding to the hole inside 31, the spot on the disk 13 becomes large for the above reason.

As shown in FIG. 11, the objective lens 5
A disk-shaped interference filter 32 (light intensity distribution switching means) is arranged on the semiconductor laser 2 side. As shown in FIG. 12, the interference filter 32 has a characteristic that, as shown in FIG. 12, the transmittance becomes maximum at the wavelength α at the time of recording, and the wavelength β at the time of reproduction hardly passes through the interference filter 32. There is. Therefore, at the time of recording, as shown in FIG. 13A, all the light beams pass through the interference filter 32, so that the light intensity distribution incident on the objective lens 5 is the same as before the incidence on the interference filter 32, but at the time of reproduction. FIG. 13 (b)
As shown in (1), the interference filter 32 reduces the light intensity of the central portion of the light flux, so that the spot exhibits a super-resolution state, which is smaller than the spot diameter at the time of recording.

In any of the above cases, the spot diameter during recording can be made relatively larger than the spot diameter during reproduction, so that the width of the pit can be increased with respect to the spot diameter during reproduction. As a result, the S / N of the reproduced signal
The ratio can be improved. However, in the above case, the required output is larger at the time of recording, so there is no output loss at the time of recording from the viewpoint that the power consumed as a whole and the maximum output of the semiconductor laser 2 can be effectively used. The latter, which applies super-resolution, is more advantageous.

The positions of the interference filters 31 and 32 can be set at arbitrary positions as long as the light beam incident on the objective lens 5 can be made to have a predetermined size. Further, since the interference filters 31 and 32 need to function only in the peripheral portion or the central portion of the light beam,
For example, the structure may be such that a filter portion is vapor-deposited on a glass plate, or the interference filters 31 and 32 may be directly fixed or vapor-deposited on the surface of the objective lens 5. Is also good. Further, it is not necessary to cut all the light beams incident on the interference filters 31 and 32 during recording. In other words, the spot diameter can be changed if there is a difference in transmittance compared with that during reproduction, so if a desired spot diameter difference can be obtained between the wavelength during recording and during reproduction, a high-pass signal can be obtained. A filter or a low pass filter may be used.

[0049]

[0050]

Magneto-optical recording and reproducing apparatus according to the invention of claim 1 according to the present invention, as described above, as the spot diameter at the time of recording becomes larger than the spot diameter during reproduction, spot irradiated onto the recording medium A spot diameter changing means for changing the diameter is provided, and the spot diameter changing means is a recording medium.
Objective lens that changes the defocus distance between the body and the objective lens
Optical drive for controlling the output of the light beam.
This beam output control means is provided with a beam output control means.
Output of the light beam emitted from the light source during recording by the step
However, the configuration is controlled according to the actual defocus distance . Therefore, the spot diameter at the time of recording can be made larger than the spot diameter at the time of reproducing. By increasing only the width of the magnetized area that is equal to or higher than the Curie temperature in the spot diameter at the time of recording with respect to the spot diameter at the time of recording, the peak temperature due to the light beam in the recording medium is not increased and Since the magnetized area occupied within the spot diameter can be increased, the quality of the reproduced signal can be improved without damaging the recording medium.

[0051] As the spot diameter varying means, at the time of reproduction at the time of record, or the use of the objective lens driving means for changing the distance between the recording medium and the objective lens. In that case, depending on the actual defocus distance at the time of record, do it by changing the output of the light beam, the recording medium can be always formed the magnetization regions with a stable width. Further claims
As described in 2 , also as a light intensity distribution switching means for switching the light intensity distribution of the light beam incident on the objective lens at the time of recording and at the time of reproducing, the spot diameter at the time of recording should be made larger than the spot diameter at the time of reproducing. Therefore, it is possible to increase the size of the magnetized area and improve the quality of the reproduced signal without fear of damaging the recording medium.

[0052] In particular, as the semiconductor laser, when using a light source wavelength is changed when increasing the output, according to claim 2
As described above, if the light intensity distribution in the optical path is changed by using a filter that selectively transmits specific wavelengths, recording and reproduction can be performed without the need for control means for changing the spot diameter. The spot diameter can be changed. Specifically, as in claim 3 , the filter has a characteristic of selectively transmitting the wavelength at the time of reproduction, and when the peripheral portion of the optical path is provided so as to be shielded in an annular shape, a diaphragm is provided at the time of recording. State and claim
As shown in 4 , when the filter has a characteristic of selectively transmitting the wavelength at the time of recording, and if it is provided so as to shield the central part of the optical path in a disk shape, super resolution will be exhibited, and all of them will be recorded. The spot diameter at the time of reproduction can be made larger than the spot diameter at the time of reproduction.

Further, in the magneto-optical recording / reproducing apparatus according to the invention of claim 5 , the light beam emitted from the semiconductor laser is condensed on the recording medium by using the objective lens as described above. In a magneto-optical recording / reproducing apparatus for recording / reproducing an information signal, an objective lens driving means for changing a defocus distance between a recording medium and an objective lens, a light beam output control means for controlling a light beam output, and a reference signal. Is provided, and a comparison means for comparing the reproduction signal with the reference signal is provided. Before recording the information signal, a recording medium and an objective lens are provided with respect to the recording medium to be recorded. By recording and reproducing the reference signal and comparing the original reference signal and the reproduced reference signal in the combination of multiple distances between Is configured to select a combination of a Do defocus distance reproduced signal is obtained and the light beam output.
Therefore, even if the optimum recording condition changes due to variations in temperature or composition of the recording medium, the recording condition that gives the best reproduction signal from a plurality of recording conditions is set in advance in the recording environment. Will always be selected,
This has an effect of enabling recording of a high quality information signal.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a relationship between a spot diameter and a light beam output according to the present invention.

FIG. 2 is a schematic diagram showing a configuration example of an optical system of a magneto-optical recording / reproducing device according to the present invention.

FIG. 3 is an explanatory diagram showing an example of a circuit adjustment method in FES.

FIG. 4 is an explanatory diagram of the FES detection method.

FIG. 5 is an explanatory diagram showing another example of a circuit adjustment method in FES.

FIG. 6 is an explanatory diagram showing another example of a circuit adjustment method in FES.

FIG. 7 is a schematic diagram showing another configuration example of the optical system of the magneto-optical recording / reproducing apparatus according to the present invention.

8 is a schematic diagram showing the outline of an interference filter used in the magneto-optical recording / reproducing apparatus shown in FIG.

9 is a graph showing a transmission frequency characteristic of an interference filter used in the magneto-optical recording / reproducing apparatus shown in FIG.

10 is a schematic diagram showing a transmission state of a light beam when an interference filter having the characteristics shown in FIG. 9 is used.

FIG. 11 is a schematic view showing still another configuration example of the optical system of the magneto-optical recording / reproducing apparatus according to the present invention.

12 is a graph showing a transmission frequency characteristic of an interference filter used in the magneto-optical recording / reproducing apparatus shown in FIG.

13 is a schematic diagram showing a transmission state of a light beam when an interference filter having the characteristics shown in FIG. 12 is used.

14A and 14B are views for explaining the relationship between a spot and a pit at the time of recording, FIG. 14A is an explanatory diagram showing a light intensity distribution in the spot, and FIG. 14B is a diagram showing a pit formed on a recording medium. It is explanatory drawing which shows the temperature distribution at the time of.

FIG. 15 is a schematic diagram showing the relationship between spots and pits during reproduction in a conventional magneto-optical recording / reproducing apparatus.

FIG. 16 is an explanatory diagram showing changes in the temperature distribution of the recording medium when the output of the light beam incident on the objective lens is increased.

[Explanation of symbols]

1 Light Beam 2 Semiconductor Laser 3 Collimating Lens 4 Polarizing Beam Splitter 5 Objective Lens 6 Objective Lens Driving Mechanism (Spot Variable Means / Objective Lens Driving Means) 9 Light-Receiving Element 11 Focus Servo Circuit (Spot Variable Means / Objective Lens Driving Means) 12 Tracking Servo circuit 13 Disc (recording medium) 20 Current-voltage conversion circuit 21 Current-voltage conversion circuit 22 Balance adjustment circuit 23 Subtraction circuit 24 Microcomputer 25 Tracking servo gain adjustment circuit 26 Comparator 27 APC circuit 31 Interference filter (light intensity distribution switching means) 32 Interference filter (light intensity distribution switching means)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ identification code FI G11B 7/135 G11B 7/135 Z (58) Fields investigated (Int.Cl. ⁷ , DB name) G11B 11/10-11 / 105 G11B 7/12-7/22

Claims (5)

(57) [Claims] 1. A light source is used to emit light using an objective lens.
An information signal is recorded on the recording medium by focusing the light beam on the recording medium.
In a magneto-optical recording / playback device that performs recording / playback, the spot diameter during recording is larger than the spot diameter during playback.
So that the spot diameter irradiated on the recording medium is large.
A spot diameter changing means for changing the size is provided. As the spot diameter changing means, a recording medium and an objective lens are used.
Objective lens drive means for changing the defocus distance between
And a light beam output control means for controlling the output of the light beam is provided.
The light beam output control means controls the light source during recording.
The output of the light beam emitted from the
Magneto-optical recording / reproducing apparatus characterized by being controlled according to
Place 2. A magneto-optical recording / reproducing apparatus for recording / reproducing an information signal on / from a recording medium by condensing a light beam emitted from a light source onto the recording medium by using an objective lens. as but greater than the spot diameter during reproduction, the spot diameter varying means are provided for changing the size of the spot diameter to be irradiated onto the recording medium, as the spot diameter varying means, at the time of reproduction and recording, versus
The light intensity distribution of the light beam incident on the object lens
A light intensity distribution switching means is provided, and a semiconductor laser is used as a light source.
The optical path from the light source to the objective lens as the degree distribution switching means
When recording or to block part of the optical path,
Filter that selectively transmits any wavelength during playback
A magneto-optical recording / reproducing device characterized by being provided with . 3. The filter selectively selects a wavelength during reproduction.
Has the property of transmitting light through the
The magneto-optical recording / reproducing apparatus according to claim 2, wherein the magneto-optical recording / reproducing apparatus is provided so as to shield in an annular shape . 4. The filter selectively selects a wavelength for recording.
Has the property of transmitting light to the center of the optical path.
The magneto-optical recording / reproducing apparatus according to claim 2, wherein the magneto-optical recording / reproducing apparatus is provided so as to shield the disk . 5. A light source is used to emit light using an objective lens.
An information signal is recorded on the recording medium by focusing the light beam on the recording medium.
In a magneto-optical recording / playback device that performs recording / playback, the spot diameter during recording is larger than the spot diameter during playback.
So that the spot diameter irradiated on the recording medium is large.
And a recording medium and an objective lens as the spot diameter changing means.
Objective lens driving means for changing the defocusing distance between
And a light beam output control means for controlling the output of the light beam
And a reference signal generating means for outputting a reference signal and a comparing means for comparing the reproduction signal with the reference signal.
Is and, before recording an information signal, on a recording medium, a recording medium
When setting multiple defocus distances between the objective lens and
Based on the combination with multiple light beam outputs
The signal is recorded and played back, and the original reference signal and the played back
Compared with the quasi signal, the focus that gives the best reproduced signal
Information communication is achieved by combining point deviation distance and light beam output.
A magneto-optical recording / reproducing apparatus, which records information.