JPH1092033A - Optical information recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a high quality reproducing without making an increase in the cost by effectively utilizing the light quantity of the heating spot of the device which employs magnetic wall movement for a reproducing. SOLUTION: The luminous fluxes from semiconductor lasers 1 and 2 having wavelengths λ1 and λ2 are synthesized by a diachroic mirror 3, converged by an objective lens 5, a recording, reproducing and heating spot is formed on a recording medium 6 and an information reproducing is conducted. Then, the magnetic wall of the medium 6 is moved by the spot, the magnetic domain is increased, a single domain is placed within the spot and the information is reproduced using the light beams from the spot. The polarization direction of the fluxes corresponds to a track direction. Note that the following conditions are set: 3.2-2.6×ln(α)>=D2 /W2 >=1.0-1.2×ln(α), α=(λ2 /λ1 )×(D1 /D2 ) where D1 is the radius of the recording and reproducing luminous fluxes taken in by the lens 5, D2 is the radius of the heating luminous fluxes taken in by the lens 5 and W2 is the effective radius in the track cross corresponding direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording / reproducing technique, and more particularly to expanding a magnetic domain by moving a magnetic wall using a heating light spot (heat light spot). And an optical information recording / reproducing apparatus in which a reproducing light spot is disposed.

[0002]

2. Description of the Related Art In recent years, in an optical information recording / reproducing apparatus using an optical information recording medium such as a magneto-optical disc,
Research and development on technology for recording and reproducing information at a higher density has been actively conducted. Conventionally, the size of a data mark carrying recorded information on a recording medium has been limited by the diffraction limit of an optical system. Recently, an optical information recording / reproducing method has been proposed in which the size of a data mark is not limited by the diffraction limit of an optical system.

[0003] For example, in Japanese Patent Application Laid-Open No. 6-290496, a magnetic domain is enlarged by moving a magnetic domain wall with a heating light spot for heating, and a reproducing light spot is arranged in the enlarged magnetic domain, so that the resolution of an optical system is increased. It has been proposed to reproduce recording information of the following minute marks to increase the recording density of a recording medium.

FIG. 7 is a schematic view of an optical head optical system of the recording / reproducing apparatus described in the above publication. In this recording / reproducing device,
As shown in the figure, a heating laser is added to the optical system of a general magneto-optical disk recording / reproducing apparatus. That is,
In FIG. 7, reference numeral 1 denotes a recording / reproducing laser light source, which emits a laser beam having a wavelength of 780 nm. Reference numeral 2 denotes a laser light source for heating, from which laser light having a wavelength of 1.3 μm is emitted. Reference numeral 3 denotes a dichroic mirror designed to transmit 780 nm light at 100% and reflect 1.3 μm light at 100%. Reference numeral 4 denotes a polarizing beam splitter, which is designed so that P-polarized light of 780 nm light and 1.3 μm light transmits 70 to 80% and S-polarized light reflects 100%. The luminous flux diameter of the 1.3 μm light is set smaller than the opening diameter of the objective lens 5 so that the NA is smaller than that of the 780 nm light collected through the entire opening of the objective lens 5. It is. Reference numeral 7 denotes a dichroic mirror arranged to prevent 1.3 μm light from leaking into the signal detection system, and is designed to transmit 100% of 780 nm light and reflect 100% of 1.3 μm light. I have. Reference numeral 6 denotes a magneto-optical recording medium.

FIG. 8 is a view for explaining the operation of a recording / reproducing apparatus having the above-described optical head optical system. As shown in FIG. 8A, a recording / reproducing spot 11 and a heating spot 12 having a diameter larger than the recording / reproducing spot 11 are formed on the land 15 between the guide grooves 14 with respect to the recording medium 6. By forming an image and moving the recording medium 6 in the direction of the arrow, a temperature distribution as shown in FIG. Thus, a desired temperature gradient as shown in FIG. 8B is formed in the area within the recording / reproducing spot 11 on the recording surface of the moving medium. Here, the isotherm 16 is an isotherm of the temperature Ts. The magnetic layer of this medium is
A first magnetic layer, a second magnetic layer, and a third magnetic layer are sequentially stacked, and a domain wall 13 is formed at a boundary between regions in which spin directions are opposite to each other. When the domain wall 13 in the first magnetic layer is at the position Xs of the medium, the medium temperature has risen to a temperature Ts near the Curie temperature of the second magnetic layer at this position. The exchange coupling with the magnetic layer No. 3 is broken. As a result, the domain wall 13 in the first magnetic layer moves almost instantaneously to a region where the temperature is higher (the domain wall energy density is small).

The domain wall 1 is located under the reproducing light beam spot 11.
When 3 passes, all the atomic spins of the first magnetic layer in the spot 11 are aligned in one direction. Each time the domain wall 13 comes to the position Xs with the movement of the medium, the domain wall 13 instantaneously moves below the spot, the direction of the atomic spin in the spot is reversed, and all are aligned in one direction. As a result, the reproduction signal amplitude is always constant and the maximum amplitude irrespective of the interval between recorded domain walls (that is, the recording mark length).

The reflected light from the reproducing light beam spot 11 undergoes rotation of the polarization plane by the magneto-optical effect, reaches the polarization beam splitter 4 via the objective lens 5, where the S-polarized component is reflected, and the dichroic mirror 7 And is guided to a signal detection system.

[0008]

However, in the case of the above-mentioned conventional example, that is, in the case of simply obtaining a heating spot with a long wavelength and a small NA, especially in a direction perpendicular to the track direction (media moving direction). There is a large waste in the direction (in the cross-track direction), which may lead to an insufficient light quantity of the heating spot 12.

That is, in the above conventional example, when the heating spot is not used, the intensity of the reproducing spot is about 3 mW, while when the heating spot is used, the intensity of the reproducing spot is 1 mW. Have been. On the other hand, the intensity of the reproducing spot in a normal case is about 1 to 1.5 mW. Therefore, the intensity density of the heating spot of the conventional example is about two to three times the intensity density of the normal reproduction spot.

In the above conventional example, the heating spot 12 has a shape similar to the substantially isotropic reproduction spot 11, and its outer diameter is about four times that of the reproduction spot 11. Therefore, the heating spot 12 is the reproduction spot 1
When the light amount is equal to 1, the intensity is about 1/16 of the intensity density of the reproduction spot 11. Therefore, heating spot 1
The intensity of 2 needs to be approximately 32 to 48 times the intensity of the reproduction spot 11 in order to obtain the intensity density of approximately 2 to 3 times. Even if the optical efficiency of the heating light projection optical system is about twice the optical efficiency of the reproduction light projection optical system, the heating power needs to be about 16 to 24 times that of the reproduction light emission power of the light source. It is.

In a normal case, the output power of the reproducing light source is 3
５5 mW. Therefore, in the above-mentioned conventional apparatus, the emission power of the heating light source needs to be about 48 to 120 mW. However, considering that the emission power of the writing light source for an optical disk device is generally 35 to 50 mW, there is a great possibility that the light intensity of the heating spot will be insufficient.

Also, if a high-output light source is used, it is difficult to manufacture such a light source, which may lead to a large increase in cost.

In view of the above circumstances, it is an object of the present invention to control a heating spot of an optical information recording / reproducing apparatus using the above-mentioned reproducing principle so that the spot is not wasted with respect to a track crossing direction. It is an object of the present invention to provide an optical information recording / reproducing apparatus which can effectively utilize the light amount of a spot and can realize good recording / reproducing without increasing the cost.

[0014]

According to the present invention, in order to achieve the above object, a light beam from a first light source and a second light source is condensed and formed on an information recording medium. In an optical information recording / reproducing apparatus for reproducing information using a first light spot and a second light spot, a domain wall involved in formation of recorded information on the recording medium is moved by the second spot, and the domain wall is moved. The magnetic domain surrounded by is expanded so that only the magnetic domain is positioned in the first light spot, and information is reproduced by light from the first light spot. The polarization direction of the light beam to be formed is a direction optically corresponding to the track direction, the diameter at which the light beam of wavelength λ ₁ forming the first spot is taken into the objective lens is D ₁ , and the polarization direction of the second spot is Waves forming The diameter at which the light beam of length λ ₂ is taken into the objective lens is D ₂ , and the dimension in the direction corresponding to the cross-track direction of the light beam diameter corresponding to 1 / e ² of the peak intensity of the light beam forming the second spot is W. _{As 2} , 3.2-2.6 × ln (α) ≧ D ₂ / W ₂ ≧ 1.0−
An optical information recording / reproducing apparatus characterized by substantially satisfying the following relationship: 1.2 × ln (α) α = (λ ₂ / λ ₁ ) × (D ₁ / D ₂ ).

Further, according to the present invention, a first light beam formed on an information recording medium by condensing light beams from a first light source and a second light source to achieve the above object. In an optical information recording / reproducing apparatus for reproducing information using a spot and a second light spot, a domain wall involved in formation of recorded information on the recording medium is moved by the second spot and is surrounded by the domain wall. The magnetic domain is enlarged and the first
Position only the magnetic domain within the light spot of
Information is reproduced by the light from the light spot, the polarization direction of the light beam forming the second spot is a direction optically corresponding to the track direction, and the first spot is formed. The diameter at which the luminous flux of the wavelength λ ₁ to be captured is taken into the objective lens is D ₁ , the diameter at which the luminous flux of the wavelength λ ₂ forming the second spot is taken into the objective lens is D ₂ , and the second spot is formed. Assuming that the dimension in the direction corresponding to the cross-track direction of the light beam diameter equivalent to 1 / e ² of the peak intensity of the light beam is W ₂ , 2.4-1.9 × ln (α) ≧ D ₂ / W ₂ ≧ 1. 5-
1.6 × ln (α) An optical information recording / reproducing apparatus characterized by substantially satisfying the following relationship: α = (λ ₂ / λ ₁ ) × (D ₁ / D ₂ ).

In one embodiment of the present invention, D ₁ ≧ D ₂ .

In one embodiment of the present invention, light beams from the first light source and the second light source are combined by a light beam separating / combining means and then condensed by one objective lens. .

In one embodiment of the present invention, the wavelength of the light beam emitted from the first light source and the wavelength of the light beam emitted from the second light source are different from each other, and the light beam separating / combining means is a dichroic mirror.

In one embodiment of the present invention, a second collimator is arranged between the second light source and the light beam separating / combining means.

In one aspect of the present invention, a polarizing beam splitter is disposed between the first light source and the light beam splitting / combining means, and light from the first light spot is emitted by the polarizing beam splitter. It is configured to be separated from light from the first light source and guided to a signal detection system.

In one embodiment of the present invention, a first collimator is disposed between the first light source and the polarizing beam splitter.

In one embodiment of the present invention, the first light source and the second light source are semiconductor lasers.

In one embodiment of the present invention, the far field pattern of the second light source is elongated in a direction corresponding to a track crossing direction of the recording medium.

[0024]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic view of an optical head according to an embodiment of the optical information recording / reproducing apparatus of the present invention. 1 is a semiconductor laser for information recording (including information erasing) and reproducing.
A laser beam having a wavelength λ ₁ (for example, 680 nm) is emitted.
Reference numeral 2 denotes a semiconductor laser for heating, which has a wavelength λ ₂ (eg, 780).
nm). 3. 100% λ ₁ light
Transmitted, a dichroic mirror designed to lambda ₂ light to reflect 100%. 24 is a polarization beam splitter having a beam shaping function, P-polarized light with respect to lambda ₁ light 70-80% transmitted and S-polarized light is designed to reflect 100%.

The laser beams emitted from the lasers 1 and 2 have a polarization plane direction such that they enter the polarization beam splitter 24 and the dichroic mirror 3 as P-polarized light. This is a direction corresponding to the track direction of the medium 6.

The focal length of the collimator 21 is 6 mm, the effective diameter (D ₁ ) of the objective lens 5 is φ3.3 mm, N
A is 0.55. The beam shaping ratio of the polarizing beam splitter 24 having a beam shaping function is approximately 2.0. The wavelength λ _{1 of the} laser 1 is 680 nm, and the far field pattern of the laser 1 has a full-width at half maximum (θ) of 11 ° in the polarization (P-polarized) direction (corresponding to the track direction), and
The full width at half maximum (θ ′) in the direction perpendicular to that is 22 °.
The recording / reproducing spot formed by the recording / reproducing light projecting optical system is substantially isotropic and has a diameter of about φ1.1 μm.
It is.

Semiconductor laser 2 for heating and collimator 2
The specifications of the heating light projecting optical system including No. 2 are set as follows.

First, the spot size required when used for heating will be described. FIG. 2 shows the relationship between the intensity distribution of light incident on the moving (rotating) recording medium 6 and the temperature distribution formed thereon when viewed in a cross section in the track direction. In FIG. 2, the solid line is the temperature distribution, and the dotted line is the intensity distribution. FIG. 2 shows that the temperature distribution on the rear side in the medium moving direction is similar to the profile of the incident light intensity distribution. On the other hand, in order to form a temperature gradient such that the direction of spin becomes uniform in the reproducing spot as a result of domain wall movement, the reproducing spot is included in at least the gradient temperature distribution on the rear side in the medium moving direction. It is necessary. Therefore, the spread of the temperature distribution on the rear side in the medium moving direction is expressed by (heating spot diameter /
It suffices that the relationship of 2) ≧ reproducing spot diameter substantially holds. That is, by doing so, it becomes possible to arrange the reproducing spot on the slope (gradient) on the rear side in the medium moving direction of the temperature distribution obtained by the heating spot. Direction of the atomic spin of the magnetic film that contributes to the reproduction of magnetic flux (corresponding to the direction of magnetization)
Can be reversed so that they are all aligned in one direction.
Thus, the magnetic domain wall involved in the formation of recorded information on the recording medium 6 is moved by the heating spot, the magnetic domain surrounded by the magnetic wall is enlarged, and only a single magnetic domain is located in the reproducing spot.

In the intensity distribution of the emitted light of the semiconductor laser, the ratio between the half width in the polarization direction and the half width in the direction perpendicular thereto is generally 1/3 to 1/2.

The recording / reproducing spot is substantially isotropic (circular) by shaping the beam or securing the clearance at the collimator 21 so as to substantially eliminate the influence of the half-width ratio. Then, the diameter of the recording / reproducing light beam incident on the objective lens 5 (1 / e ² of the peak value of the intensity distribution of the light beam).
The diameter of the above part: in the case of a semiconductor laser, the polarization direction differs from the direction perpendicular to the polarization direction), and W
The diameter of the luminous flux passing through (taken into the objective lens 5) is D
Then, D / W is approximately 0.85 or less.

The beam for heating is introduced into the objective lens 5 in such a form as to reflect the above half-width ratio without shaping the beam and as little as possible in the collimator 22. At this time, if the polarization direction of the light beam is made parallel to the track direction of the medium, an oblong spot long in the track direction is obtained. This makes it possible to effectively use the amount of light in a direction perpendicular to the track direction (traverse direction of the track).

FIG. 3 shows the spot diameter in the direction parallel to the track direction, based on the diameter of the isotropic reproduction spot obtained when D / W ≒ 0.85. Here, the spot diameter is defined as D / W ≒ 0.
Reference is made to the time of 85 and the ratio is shown. In FIG. 3, the solid line is when the half width ratio is ３, and the dotted line is when the half width ratio is ２. When the spot diameter ratio is doubled, when the half width ratio is 1/3, D / W ≒ 1.0 (in the figure, D / W corresponds to a direction perpendicular to the track direction). D / W ≒ 1.5 when the half width ratio is １ ／. Therefore,
If D / W is 1.0 or more, preferably 1.5 or more,
There is no problem with the size of the heating spot.

Regarding the optical efficiency, in the recording / reproducing light projecting optical system which passes from the semiconductor laser 1 through the collimator 21, the polarizing beam splitter 24 and the objective lens 5, as in the case of the ordinary magneto-optical optical head. About 40%. On the other hand, the collimator 22
In the projection optical system for heating that passes through the objective lens 5, since the polarizing beam splitter does not exist, the collimator 2
2, the loss can be made relatively small, so that about 60-80%, that is, about 2-3 times of the recording / reproducing optical system is possible.

Next, regarding the light intensity required on the recording medium, the power at the time of recording is about 6 to 10 times the power at the time of reproduction. As described above, the power at the time of heating is about two to three times the power at the time of reproduction. Therefore, since the light source is limited by the power at the time of recording, the heating light source may have the same specifications as those of the light source for a normal magneto-optical disk, and it is efficient to use one.
It may be about ４ to ４. Therefore, the heating spot has an intensity density 2-3 times that of the reproduction spot,
If the spot diameter is enlarged by a margin on the optical efficiency, it is possible to increase the area to 6 to 10 times the area of the reproducing spot.

FIG. 4 shows the spot area based on the isotropic reproduction spot obtained when D / W ／ 0.85. Here, the spot area is shown as a ratio with respect to the case where the D / W of the reproducing light beam is 0.85. In FIG. 4, the solid line is when the half width ratio is １ ／, and the dotted line is when the half width ratio is ２. Looking at the spot area ratio of 8 times, when the half width ratio is 1/3, D
/W≒2.4, and D / W ≒ when the half width ratio is １ ／.
3.3. Therefore, when D / W is 3.3 or less, preferably 2.4 or less, there is no problem in terms of intensity density as a heating spot.

As described above, a necessary light amount can be secured without wasting light in the cross-track direction, and a temperature gradient is formed such that the spin direction becomes uniform in the reproducing spot as a result of the domain wall movement. As a heating spot, the polarization direction of the heating spot is parallel to the track direction of the recording medium, and the objective lens passing diameter D of the light beam of the heating spot in the cross-track direction is used.
In addition, the incident light beam diameter W may be about 3.3 ≧ D / W ≧ 1.0, preferably about 2.4 ≧ D / W ≧ 1.5.

This condition is the same for regeneration and heating.
This is the case. In the case as shown in FIG.
The light flux is separated from the light flux for recording and reproduction by the dichroic mirror 3.
Λ₁ ≠ λ_Two It is. Great for heating
To get a spot, λ ₁ <Λ_Two Is more convenient
And the diameter of the luminous flux taken into the objective lens 5
D for playback₁ D for heating_Two Then D₁ > D_Two When
It is more advantageous to do so. On the other hand, in such a case,
Objective lens NA is D₁ , D_Two Is proportional to Therefore, play
The heating spot diameter is based on the heating spot diameter.
(Spot diameter for reproduction) x (λ_Two / Λ₁ ) × (D₁ / D
_Two ), And the vertical axis in FIG. 3 is a factor α = [(λ_Two/ Λ₁ ) ×
(D₁ / D_Two )] And the vertical axis in FIG. 4 is the area.
And the factor α^Two It takes.

Incidentally, the parameter D / W determines the intensity distribution of the luminous flux (taken through the objective lens) taken into the objective lens as an argument of the exponential function. The intensity distribution of the image spot formed by the objective lens is determined by the intensity distribution of the light beam taken into the objective lens, and the Fourier transform of the exponential function is almost exponential because it is an exponential function. Therefore, the factors α and α ² are
The parameter D / W is involved in the form of natural logarithm with α and α ² as arguments. Therefore, D / W in the cross-track direction (displayed as "D / Wlower" in the sense of the lower limit thereof) is shown using ln (α) as a variable under the condition that (heating spot diameter / 2) = reproducing spot diameter. When the half width ratio is 1/2 (dotted line), D / Wlowerlow-1.18 × ln (α) +1.03 When the half width ratio is 1/3 (solid line). ) Is D / Wlower ≒ −1.61 × ln (α) +1.52. Then, under the condition that the spot area is eight times as large as the spot area, D / W in the track cross direction is used with ln (α) as a variable.
(Displayed as "D / Wupper" in the sense of its upper limit)
FIG. 6 shows that when the half width ratio is ≒ (dotted line), D / Wupper 半 −2.59 × ln (α) +3.18 when the half width ratio is ３. At the time (solid line), D / Wupper ≒ -1.93 × ln (α) +2.36.

From the above, it is possible to secure a required light amount without wasting light in the cross-track direction, and to form a temperature gradient such that the direction of spin becomes uniform in the reproducing spot as a result of domain wall movement. Then, about the heating spot,
When the polarization direction is not parallel to the track direction of the recording medium 6 and the diameter of the heating spot light beam passing through the objective lens and the incident light beam diameter in the cross-track direction are D ₂ and W ₂ , respectively, 3.2-2.6. × In (α) ≧ D ₂ / W ₂ ≧ 1.0−
1.2 × ln (α) desirably 2.4-1.9 × ln (α) ≧ D ₂ / W ₂ ≧ 1.5−
1.6 × ln (α) is substantially satisfied.

Based on the above, the heating laser 2 and the collimator 22 of the optical system shown in FIG. 1 were selected. Specific examples of the numerical values are shown below. Wavelength λ of heating laser 2
₂ is 780 nm. Let the focal length of the collimator 22 be f
Indicated by _col . Incidentally, D _2, when the effective diameter larger than the objective lens 5, was assumed equal to the effective diameter of the objective lens 5.

Concrete Example 1 θ = 12 ° θ ′ = 24 ° f _col = 6 mm D ₂ = 1.65 W ₂ = 1.07 D ₂ / W ₂ = 1.55 Spot diameter ratio in track direction = 3.6 tracks Transverse direction spot diameter ratio = 1.3 Spot area ratio = 3.0 Specific example 2 θ = 9 ° θ ′ = 27 ° f _col = 6 mm D ₂ = 1.65 W ₂ = 0.80 D ₂ / W ₂ = 2.06 Spot diameter ratio in track direction = 3.2 Spot diameter ratio in cross track direction = 1.6 Spot area ratio = 7.7 Specific example 3 θ = 12 ° θ ′ = 24 ° f _col = 7 mm D ₂ = 1. 49 W ₂ = 1.24 D ₂ / W ₂ = 1.19 Spot diameter ratio in the track direction = 2.9 Spot diameter ratio in the cross track direction = 1.3 Spot area ratio = 3.2 Specific example 4 θ = 9 ° θ _{'= 27 ° f col = 7mm} D 2 = 1.49 W 2 = 0.93 D 2 / W 2 = 1.59 track direction spot In this example, the spot diameter in the track transverse direction is 1.3 to 1.6 times the spot for reproduction. In view of the fact that the spot diameter in the polarization direction is made twice or more, there is almost no waste of light quantity. The spot diameter in the polarization direction (track direction) is 2.6 to 3.6 times the spot for reproduction,
A sufficient temperature gradient for domain wall motion reproduction can be formed. Further, the spot area is 3.0 times that of the reproduction spot.
It is about 7.7 times, and if this is the case, a sufficient amount of light required as a heating spot can be secured.

[0043]

As described above, according to the present invention, the domain wall is moved by the heating spot so that the resultant spin direction is uniform in the reproducing spot, and the minute recording is performed. In the mark reproducing device, by setting the optical system parameters within a predetermined range, the light amount of the heating spot is effectively used, and the light amount in the cross-track direction is wasted, and good recording and reproducing can be performed without increasing the cost. Can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic view of an optical head according to an embodiment of an optical information recording / reproducing apparatus of the present invention.

FIG. 2 is a graph showing a comparison between a temperature profile on a recording medium and an incident intensity distribution shape of a heating spot.

FIG. 3 is a graph showing a change in a track-to-track diameter ratio of a heating spot relative to D / W with respect to a reproduction spot.

FIG. 4 is a graph showing a change in an area ratio of a heating spot with respect to a reproduction spot with respect to D / W.

FIG. 5 is a graph showing a change in a lower limit value of D / W.

FIG. 6 is a graph showing a change in an upper limit value of D / W.

FIG. 7 is a schematic diagram of an optical head optical system of a conventional recording / reproducing apparatus.

FIG. 8 is a diagram for explaining the operation of a conventional recording / reproducing device.

[Explanation of symbols]

 Reference Signs List 1 semiconductor laser for recording / reproducing 2 semiconductor laser for heating 3 dichroic mirror 4 polarizing beam splitter with beam shaping function 5 objective lens 6 recording medium 11 reproducing spot 12 heating spot 13 domain wall 14 guide groove 15 land 21 recording / reproducing collimator 22 heating Side collimator 24 Polarizing beam splitter

Claims (10)

[Claims] An optical system for converging light beams from a first light source and a second light source to reproduce information using a first light spot and a second light spot formed on an information recording medium. A magnetic information recording / reproducing apparatus, wherein a magnetic domain wall involved in formation of recording information on the recording medium is moved by the second spot to expand a magnetic domain surrounded by the magnetic domain wall, and only the magnetic domain is included in the first light spot. Positioned to reproduce information with light from the first light spot, wherein a polarization direction of a light beam forming the second spot is a direction optically corresponding to a track direction; The diameter at which the light beam of wavelength λ ₁ forming the first spot is taken into the objective lens is D ₁ , the diameter at which the light beam of wavelength λ ₂ forming the second spot is taken into the objective lens is D ₂ , The second sport The dimension corresponding to the track crossing direction of the 1 / e ² equivalent beam diameter of the peak intensity of the light flux forming the door as _{W 2, 3.2-2.6 × ln (α} ) ≧ D 2 / W 2 ≧ 1.0−
An optical information recording / reproducing apparatus, wherein a relationship of 1.2 × ln (α) α = (λ ₂ / λ ₁ ) × (D ₁ / D ₂ ) is substantially established. 2. An optical system for converging light beams from a first light source and a second light source to reproduce information using a first light spot and a second light spot formed on an information recording medium. A magnetic information recording / reproducing apparatus, wherein a magnetic domain wall involved in formation of recording information on the recording medium is moved by the second spot to expand a magnetic domain surrounded by the magnetic domain wall, and only the magnetic domain is included in the first light spot. Positioned to reproduce information with light from the first light spot, wherein a polarization direction of a light beam forming the second spot is a direction optically corresponding to a track direction; The diameter at which the light beam of wavelength λ ₁ forming the first spot is taken into the objective lens is D ₁ , the diameter at which the light beam of wavelength λ ₂ forming the second spot is taken into the objective lens is D ₂ , The second sport The dimension corresponding to the track crossing direction of the 1 / e ² equivalent beam diameter of the peak intensity of the light flux forming the door as _{W 2, 2.4-1.9 × ln (α} ) ≧ D 2 / W 2 ≧ 1.5−
1.6 × ln (α) An optical information recording / reproducing apparatus characterized by substantially satisfying the following relationship: α = (λ ₂ / λ ₁ ) × (D ₁ / D ₂ ). 3. The optical information recording / reproducing apparatus according to claim 1, wherein D ₁ ≧ D ₂ . 4. The light beam from the first light source and the second light source is combined by a light beam separating / combining means and then condensed by one objective lens. The optical information recording / reproducing apparatus according to claim 1. 5. The wavelength of a light beam emitted from the first light source and the wavelength of a light beam emitted from the second light source are different from each other, and the light beam separating / combining means is a dichroic mirror. Item 5. The optical information recording / reproducing device according to Item 4. 6. An optical information recording apparatus according to claim 4, wherein a second collimator is disposed between said second light source and said light beam separating / combining means. Playback device. 7. A polarizing beam splitter is disposed between the first light source and the light beam separating / combining means, and light from the first light spot is separated from the first light source by the polarizing beam splitter. The optical information recording / reproducing apparatus according to any one of claims 4 to 6, wherein the optical information recording / reproducing apparatus is configured to be separated from the light and guided to a signal detection system. 8. The optical information recording / reproducing apparatus according to claim 7, wherein a first collimator is arranged between the first light source and the polarization beam splitter. 9. The optical information recording / reproducing apparatus according to claim 1, wherein said first light source and said second light source are semiconductor lasers. 10. The method according to claim 1, wherein the far field pattern of the second light source is elongated in a direction corresponding to a track crossing direction of the recording medium.
The optical information recording / reproducing device according to any one of the above.