JP3077426B2 - Optical information 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 an optical information recording / reproducing apparatus suitable for an information input / output device for recording / reproducing information using light.
Related to the device .

[0002]

2. Description of the Related Art FIG. 3 shows an example of a conventional super-resolution optical information recording / reproducing apparatus.

The basic configuration is as follows: a laser diode 1, which emits laser light as a laser source; a light-shielding plate 9, which blocks light near the optical axis; a beam splitter 2, which branches laser light; an objective lens 4, which focuses laser light; Akucheeta 5 for driving the objective lens, a photodiode 7 as a light receiving element for converting the return light into an electric signal.

The laser light emitted from the laser diode 1 passes through a light-shielding plate 9 having a light-shielding area near the optical axis, and becomes laser light passing near the optical axis to the beam splitter 2. The laser beam transmitted through the beam splitter 2 is focused on the information recording medium 6 by the objective lens 4. At this time, the beam diameter of the beam spot 11 can be made smaller than that of the normal spot 10 without the light shielding plate 9 due to the super-resolution effect of light shielding near the paraxial axis (φ
b <φc). The laser beam reflected by the information recording medium 6 is
It is reflected by the street beam splitter 2 through the objective lens 4 again, toward the photodiode 7. The signal is converted into an electric signal by the photodiode 7, and a reproduced signal and an error signal are obtained by a signal reproducing circuit.

With the above configuration, high-density information can be recorded and reproduced using a super-resolution light beam.

[0006]

In the configuration described above, in order to efficiently guide the return light from the information recording medium 6 to the photodiode 7 , the light-shielding plate 9 is connected to the outward path of the optical path system, that is, It must be located between the laser diode 1 and the beam splitter 2 . Therefore, when the objective lens 4 is moved in the track direction, there is a problem that the center of the light shielding plate 9 and the optical axis of the laser light are displaced, and a good super-resolution beam cannot be obtained.

FIG. 4 shows the above explanation. When the objective lens 4 moves by f as shown in FIG.
Cannot obtain a good beam.

An object of the present invention is to provide a super-resolution optical information recording / reproducing apparatus which always forms a good super-resolution beam spot even when the objective lens moves without reducing the light use efficiency. .

[0009]

According to the present invention, there is provided a laser source for emitting a laser beam.
The laser light emitted from the laser source is converted into a linearly polarized P-wave.
Separates into S wave and transmits only P wave,
The S-wave returning from the recording medium is reflected to emit the laser light source.
It has a polarization beam splitter that separates from the emission path, and a polarization wave transmission selection area that blocks only linearly polarized P waves near the optical axis.
Other than the polarized light separating plate and the polarized wave transmission selection area of the polarized light separating plate
1/4 that converts the linearly polarized P wave transmitted through the region
A polarized wave transmitting / selecting means comprising a wavelength plate, an objective lens for condensing the laser beam transmitted through the polarized wave transmitting / selecting means on an information recording medium at a super resolution, and focusing the objective lens on at least two axes of a track. Actuator that drives in the direction, and is reflected by the information recording medium,
Incident on the 波長 wavelength plate as circularly polarized light,
The plate is converted into linearly polarized S waves by the wavelength plate,
Area, and is reflected by the polarizing beam splitter.
; And a light receiving element for converting into an electric signal the separated return light from the emission optical path of the laser light source Te and
Is what you do. Further, the present invention provides the actuator
Integrates the polarized wave transmission selection means and the objective lens
Focus and drive in at least two axes of track
Or the polarization wave transmission and sorting means comprises polarization separation.
Another feature is that the plate and the quarter-wave plate are integrated.
Things.

[0010]

Next, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing an optical system according to the present invention. The laser light that has exited the laser diode 1 is split into linearly polarized P-waves and S-waves by a polarization beam splitter 2, and only the P-wave is directed to the objective lens 4. The laser light is incident on the polarized wave transmission / selection means 3 simultaneously held by the objective lens 4 and the lens holder 5 of the actuator. Here, the polarized wave transmission selection means 3 is composed of, for example, a polarized light separating plate 3a having a polarized wave transmission selection region 3c made of, for example, a polarizing film near its center, and a λ / 4 plate ( 1/1) for converting linearly polarized light into circularly polarized light. 4 wavelength plate) 3b.

At this time, the rotation axis of the polarization wave transmission and sorting means 3 is shifted with respect to the optical axis OO 'so that the linearly polarized P wave near the optical axis which enters the polarization wave transmission suitable area is completely cut off. Set the direction mounting angle. As a result, only the light other than the polarized wave transmission selection area 3c of the linearly polarized P wave is directly
b.

The linearly polarized P wave from which light near the optical axis is eliminated is transmitted to the λ / 4 plate 3b, converted into circularly polarized light, condensed by the objective lens 4, and super-resolution on the information recording medium 6. Is formed. The reflected light from the information recording medium 6 becomes circularly polarized light in the opposite direction to that at the time of incidence due to reflection, passes through the objective lens 4, and enters the polarized wave transmission selection means 3 again. Since the light enters the λ / 4 plate 3b as circularly polarized light having a direction opposite to that at the time of incidence, the light enters the polarization separation plate 3a as linearly polarized light rotated by 90 ° from that at the time of incidence, that is, in this case, an S wave.

[0013] Thus the laser beam is all light including a polarized light transmission selection area 3c is transmitted through the polarization separating plate 3a, reflections most of the light in the opposite the next polarizing beam splitter 2 to the photodiode 7 side Will do. With the above configuration, a good super-resolution beam spot is always generated even when the objective lens is moved without lowering the light use efficiency, and high-density information recording and reproduction can be realized.

FIG. 2 shows an embodiment of the integrated polarized wave transmission / selection means. In this figure, a polarized wave transmission / selection region is formed near the center of the λ / 4 plate by, for example, a polarizing film or the like. The polarization wave transmission selection means of (1) is realized.

[0015]

As described above, the present invention provides a laser source
The laser beam emitted from, first, a polarizing over beam splitter
Separates into linearly polarized P-waves and S-waves and transmits only P-waves
In addition, polarization that blocks only linearly polarized P-waves near the optical axis
Polarization separation plate having light-wave transmission selection region and polarization separation plate
Linearly polarized P wave transmitted through a region other than the polarized wave transmission selection region
Polarized wave transmission screening consisting of a quarter-wave plate that converts light into circularly polarized light
After passing through the means, the information recording medium through the objective lens
Focused at super resolution on top, and reflected by the information recording medium
The laser light is converted into circularly polarized light having a direction opposite to that of the incident light,
And a linearly polarized light S
The wave-formed return light is transmitted through the entire area of the polarization separation plate,
Later, in the polarizing beam splitter, the laser light source
Because it is configured to be separated from the output light path and guided to the light receiving element,
Just before the objective lens using the polarization of the laser light
The super-resolution effect by shading near the paraxial can be exhibited.
And an objective lens placed close to the polarized wave transmission selection means
On the information recording medium when the lens is driven in the track direction.
The effect of the formed beam diameter on the aperture effect depends on the polarization wave.
The transmission selection means is located far away from the objective lens.
Is very small compared to conventional
To always form a good super-resolution beam spot
Higher precision recording / reproduction is possible, and polarized wave transmission selection
The polarization separation plate included in another means has a linear polarization P near the optical axis.
Because it has a polarized wave transmission selection area that blocks only waves, it is close to the optical axis.
Transmission sorting where the side is a transmissive area and the periphery of the optical axis is a semi-transmissive area
Light transmission area when compared to filters etc.
Until it is proportional to the square of the radius from the optical axis
No loss of light transmittance can be minimized
Therefore, there is almost no concern about a decrease in light use efficiency,
In addition, the polarized light is
Only linearly polarized P-waves trying to pass through the transmission sorting area are blocked.
While the return is reflected by the information recording medium.
Laser light is converted to linearly polarized S waves in a quarter-wave plate
Has been changed, so that the polarization
It can pass through the whole area of the light separating plate,
Guide the return light to the light receiving element with very high efficiency
It is possible to secure light use efficiency in this regard as well.
And greatly improve the recording and reproduction accuracy of high-density signals.
It has excellent effects, such as being able to increase. Also book
The invention is characterized in that the actuator comprises the polarized wave transmission selection means.
The objective lens is integrated to reduce focus and track
Without even a structure for driving the two-axis direction treasure polarized wave Toru
Is it a physical reason to place the over-selection means close to the objective lens?
The objective lens and the polarized wave transmission selection means
Even if there is a relative misalignment on the information recording medium,
The effect of the formed beam diameter on the aperture effect is minimal.
Naturally, polarized wave transmission selection means and objective lens
This is done by integrating the
Even small effects can be eliminated, and polarized wave transmission sorting
Super-resolution effect due to light shielding near paraxial in means
Thoroughly strengthened recording / playback accuracy of high-density signals
This has the effect of being able to contribute to a significant improvement. Ma
Further, in the present invention, the polarized wave transmission / selection means comprises a polarized light separating plate and
Since the 波長 wavelength plate is integrated, the light of the polarized wave transmission
Reduce the thickness in the axial direction and make the optical information recording / reproducing device thinner.
It has effects such as being able to contribute to the total.

[Brief description of the drawings]

FIG. 1 is an optical path diagram of an embodiment of the present invention.

FIG. 2 is a view showing one embodiment of an integrated polarized wave transmission / selection means in the present invention.

FIG. 3 is an optical path diagram of a conventional super-resolution optical information recording / reproducing apparatus.

FIG. 4 is an optical path diagram illustrating a problem in the related art.

[Explanation of symbols]

1 laser diode 2 polarization beam splitter 3 polarized wave transmission selection means 3a polarized separated plate 3b lambda / 4 plate 3c polarized wave transmissive selection area 4 the objective lens 5 biaxial actuator 6 information recording medium 7 photodiode 8 1 integrated polarized wave transmission selection means Reference Signs List 9 light shielding plate 9a light shielding area 10 normal beam spot 11 super-resolution beam spot 11a main beam 11b side lobe 12 super-resolution beam spot when moving optical axis

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-2-161628 (JP, A) JP-A-4-125826 (JP, A) JP-A-63-259840 (JP, A) JP-A-1- 94544 (JP, A) JP-A-6-52573 (JP, A) JP-A-63-113220 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 7/135 G11B 7 / 00

Claims (3)

(57) [Claims] 1. A laser source for emitting laser light, and a laser beam emitted from the laser source is linearly polarized P-wave and S-polarized.
Separate into waves and allow only P-waves to pass
Emitting the laser light source by reflecting the S wave returning from the recording medium
Polarizing beam splitter that separates from the optical path and near the optical axis
Polarized light having a polarized light transmission selection region that blocks only linearly polarized P waves
Other than the light separating plate and the polarized wave transmission selection region of the polarized light separating plate
Quarter wave that converts linearly polarized P wave transmitted through a region to circularly polarized light
A polarized wave transmitting / selecting means comprising a long plate, an objective lens for condensing the laser beam transmitted through the polarized wave transmitting / selecting means on an information recording medium at a super resolution, and at least two axes of focusing and tracking the objective lens Actuator that drives in the direction, and is reflected by the information recording medium,
Incident on the 波長 wavelength plate as circularly polarized light,
The plate is converted into linearly polarized S waves by the wavelength plate,
Area, and is reflected by the polarizing beam splitter.
An optical information recording / reproducing apparatus, comprising: a light receiving element for converting return light separated from an emission optical path of the laser light source into an electric signal. 2. The apparatus according to claim 1, wherein the actuator integrates the polarized wave transmission / selection unit and the objective lens into a focus and a focus.
2. The optical information recording / reproducing apparatus according to claim 1, wherein the optical information recording / reproducing apparatus is driven in at least two axial directions of the rack . 3. The polarization wave transmission and sorting means, wherein a polarization separation plate and a 波長 wavelength plate are integrated.
The optical information recording / reproducing apparatus according to the above.