JPH05128582A - Optical information recorder/reproducer and beam shaping rise prism for the same - Google Patents

Abstract

PURPOSE:To provide a beam shaping rise prism for simplifying an optical information recorder/reproducer and the recorder/reproducer using the prism. CONSTITUTION:A beam shaping rise prism 21 starts to generate a parallel laser luminous flux from a fixing member 10 provided in a movable unit 20 toward a recording surface of an optical information recording medium 30, and shapes a sectional shape of the flux so as to form the shape of a spot to be condensed on the recording surface in a desired shape. The prism 21 has an incident surface 211 in which the flux from the member is incident, a reflecting surface 212 for internally reflecting the flux incident from the surface 211, and an irradiating surface 213 for irradiating the medium 30 with the flux reflected on the surface 212. The sectional shape of the flux from the surface 213 is shaped in a desired shape.

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 and a beam shaping rising prism used in the optical information recording / reproducing apparatus.

[0002]

2. Description of the Related Art An LD light source section for emitting a laser beam,
A fixing unit having a detection unit that detects information contained in the return light from the optical information recording medium, and a laser that is movable in the track arrangement direction of the optical information recording medium and is movable from the fixing unit. 2. Description of the Related Art An optical information recording / reproducing apparatus is known that has a movable portion that collects a light flux as a spot on a recording surface of an optical information recording medium.

In such an optical information recording / reproducing apparatus, the spot focused on the recording surface of the optical information recording medium is generally adjusted to a shape close to a circle. Since the divergence angle of laser light emitted from an LD (semiconductor laser) is different between the direction parallel to the joint surface and the direction orthogonal thereto, for example, when this is converted into a parallel laser beam, the beam cross-sectional shape is generally elliptical. Become. Therefore, in order to obtain a “substantially circular spot”, it is necessary to shape the cross section of the laser beam into a substantially circular shape between the LD and the objective lens that focuses the laser beam toward the recording surface. is there. This shaping is called "beam shaping".

Conventional beam shaping is performed by providing a dedicated "beam shaping prism" in the fixed portion (for example, Japanese Patent Laid-Open No. 24-4843), and the direction of the laser beam from the LD light source and the fixed portion. Since the directions of the laser light beams emitted from the laser beams are not parallel to each other, the fixed portion tends to be large in size, and there is a problem that it is difficult to make the optical information recording / reproducing apparatus compact.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and is a novel beam shaping start-up prism that can make an optical information recording / reproducing apparatus compact, and an optical system using this prism. The purpose is to provide an information recording / reproducing device.

[0006]

According to another aspect of the present invention, there is provided a beam shaping rising prism having an "LD light source section for emitting a laser beam and a detecting section for detecting information contained in a return beam from an optical information recording medium. A fixed part fixed at a fixed position, and a movable part movable in the track arrangement direction of the optical information recording medium and converging a laser beam from the fixed part as a spot on the recording surface of the optical information recording medium. Optical information recording
In the reproducing device, the laser beam from the fixed part provided on the movable part is launched toward the recording surface, and
It is a prism that shapes the cross-sectional shape of the laser beam in order to make the shape of the spot focused on the recording surface into a desired shape.

This beam shaping rising prism is described as follows: "An incident surface on which a laser light flux from a fixed portion is incident, a reflecting surface that internally reflects the laser light flux incident from this incident surface, and a laser reflected by this reflecting surface. And an exit surface for emitting the light beam toward the optical information recording medium, and refracting the incident surface and / or the exit surface shapes the cross-sectional shape of the light beam emitted from the exit surface into a desired shape. " Characterize.

The beam shaping rising prism is also integrated with a "two-division light receiving element for receiving the internally reflected light flux of the return light from the optical information recording medium by the incident surface and detecting the tilt of the optical information recording medium". (Claim 2).

The "optical information recording / reproducing apparatus" of claim 3 is
An optical information recording / reproducing apparatus having a beam shaping rising prism according to claim 1 or 2 in a movable portion. The movable part of the optical information recording / reproducing apparatus is provided with a message "A part of the laser light flux from the fixed part which is externally reflected by the incident surface of the beam shaping rising prism is received to detect the moving direction of the movable part and the fixed part. It is possible to provide a "light receiving means" for detecting the deviation of the direction of the laser light flux from the above. Claims 3 and 4
The optical information recording / reproducing apparatus performs recording and / or reproducing on an optical information recording medium. Therefore, the above-mentioned device may be dedicated to recording or reproduction, or may be one that performs recording and reproduction.

On the other hand, in the optical information recording / reproducing apparatus of the fifth aspect, at least reproduction is performed among recording and reproducing of optical information. That is, the apparatus of claim 5 is the device of claim 3 or 4, wherein the optical information recording medium is a "magneto-optical recording medium", and the magneto-optical Kerr effect is used for the optical information recording medium. To reproduce optical information. The feature is that "the direction of S-polarized light of the laser beam from the fixed portion is parallel to the incident surface of the beam shaping rising prism".

As described above, in the "beam shaping rising prism" of the present invention, the laser light flux from the fixed portion is
The light enters from the incident surface, is internally reflected on the reflective surface, and exits from the exit surface. Further, the reflected laser light flux (return light) from the optical information recording medium enters from the emission surface, is internally reflected on the reflection surface, and further emerges from the incidence surface to be returned to the fixed portion. Therefore, it goes without saying that the internal incident angle on the entrance / exit surface is appropriately set smaller than the critical angle of total reflection. Further, it is desirable that the internal incident angle on the reflecting surface is set to be equal to or more than the critical angle of total reflection.

[0012]

In FIG. 2, the area I is the air area and the area II is the prism internal area. As shown in FIG. 1A, when a parallel light beam having a light beam diameter: d in a plane parallel to the plane of the drawing enters a prism with an incident angle: α and is refracted at a refraction angle: β, Light flux diameter: D is D = (cos β / cos
α) · d, and since cosβ> cosα,
D> d. In the direction orthogonal to the drawing, there is no change in the beam diameter due to refraction. Therefore, when a parallel laser beam is made incident on the prism and refracted at the incident surface, the beam diameter of the refracted light becomes large only at the entrance / refraction surface.

Further, as shown in FIG. 2B, a parallel light beam having a light beam diameter D in a plane parallel to the drawing enters the prism surface at an incident angle γ in the prism, and has a refraction angle δ in the air. When the light is emitted to the area, the light flux diameter: d of the emitted light becomes smaller than the light flux diameter: D. There is no change in the luminous flux diameter in the direction orthogonal to the drawing. Therefore, when the parallel laser light beam is refracted from the prism and emitted to the air region, the light beam diameter of the emitted light becomes small only on the entrance / refraction surface.

The beam shaping rising prism of the present invention performs beam shaping by utilizing this principle.

[0015]

EXAMPLES Specific examples will be described below.

FIG. 1 (a) shows an embodiment of the apparatus according to claim 3. In the figure, reference numeral 10 indicates a fixed portion, reference numeral 20 indicates a movable portion, and reference numeral 30 indicates an optical disc as an optical information recording medium. The fixed portion 10 is fixedly provided on a stationary portion of the optical information recording / reproducing apparatus. The fixed part includes an LD light source part including an LD light source 11 and a collimator lens 13, a beam splitter 15, and a signal detection system 17. The laser light flux emitted from the LD light source 11 is collimated by the collimator lens 13, passes through the beam splitter 15, and is emitted from the fixed portion 10.

The movable portion 20 is movable in the track arrangement direction (left and right direction in the drawing) on the optical information recording medium 30 by a drive system (not shown), and a beam shaping rising prism having a shape as shown in FIG. 1B. 21 and the objective lens 2
Have three.

The parallel laser light flux from the fixed portion 10 is incident on the movable portion 20 from the incident surface 211 of the beam shaping rising prism 21, is internally reflected by the reflecting surface 212, and is emitted from the exit surface 213 to the optical axis of the objective lens 23. It is emitted as a parallel light flux and is incident on the objective lens 23, and the same lens 2
By the action of 3, the light is focused as a spot on the recording surface of the optical disc 30. When recording optical information, the emission intensity of the LD light source 11 is intensity-modulated according to the recording signal.

The reflected light from the recording surface passes through the objective lens 23 in the opposite direction, enters the beam shaping rising prism 21 from the exit surface 213, is reflected by the reflecting surface 212, exits from the entrance surface 211, and returns as return light. It is incident on the fixed portion 10. This return light is bent by the beam splitter 15 so that its optical path is directed to the signal detection system 17.

The signal detection system 17 outputs various information that incident return light has, that is, a tracking error signal and a focusing error signal when recording optical information, and an information signal in addition to these error signals when reproducing. To detect. In accordance with the tracking error signal, the movable portion is displacement-adjusted in the left-right direction in the figure to perform tracking control. Further, according to a focusing error, the objective lens 23 is displaced and adjusted in the optical axis direction by a focusing servo mechanism (provided on the movable portion), which is not shown, to perform focusing control.

In this embodiment, the exit surface 213 of the beam shaping rising prism 21 is orthogonal to the optical axis of the objective lens 23, and the parallel laser beam from the fixed portion 10 is exited so as to be orthogonal to the exit surface 213. .. The incident surface 211 is inclined with respect to the direction of the parallel laser light flux from the fixed portion 10, and when the parallel laser light flux enters the beam shaping rising prism 21, it is refracted by the incident surface 211, and
The light beam diameter expands in the plane of (a). The cross-sectional shape of the parallel laser light flux traveling from the fixed portion 10 side to the movable portion is shown in FIG.
It has an elliptical shape as shown in (c). The major axis direction of the elliptical shape in FIG. 1C corresponds to the direction orthogonal to the drawing in FIG. Therefore, the beam cross section of the parallel laser beam incident from the incident surface 211 of the beam shaping rising prism 21 is enlarged only in the single axis direction of FIG.
As shown in (d), it has a substantially circular cross-sectional shape, and ejects from the emission surface 213 while maintaining this cross-sectional shape. Therefore, the shape of the spot on the recording surface is also substantially circular.

Next, an embodiment of the apparatus according to claim 5 will be described. In this case, the optical disc 30 in FIG. 1A is of the magneto-optical recording type. When the optical information is magnetically recorded by the apparatus shown in FIG. 1, it is the same as the conventionally known writing of magneto-optical recording. That is, a uniform magnetic field is applied from the outside to the focus position of the spot by a magnetic generator (not shown) to modulate the emission intensity of the LD light source 10 according to the recording signal.

In order to implement the invention of claim 5 with the apparatus of FIG. 1A, as shown in FIG. 4A, the beam shaping rising prism 21 is made incident on the incident surface from the fixed portion side. The direction of polarization of the S-polarized parallel laser beam is
Be parallel to 1. Depending on the magnetization characteristics of the portion focused as a spot by the objective lens, the reflected laser light flux undergoes a rotation of the polarization plane due to the magneto-optical Kerr effect.

That is, as shown in FIG. 4B, the plane of polarization of the reflected light turns from the S-polarized state by an angle of θ to become a luminous flux having a P-polarized component. Therefore, when the fluctuation of the P-polarized component in the return light is detected, it becomes the reproduction signal.

By the way, when the light reflected from the recording surface is transmitted through the beam shaping rising prism in the opposite direction, the exit surface 2
13, the reflecting surface 212, and the incident surface 211 move backward. At this time, external reflection occurs on the exit surface 213, and internal reflection occurs on the reflecting surface 212 and the entrance surface 211. The reflectance of external reflection on the prism surface is generally as shown in FIG. 3A, and the reflectance of internal reflection is as shown in FIG. 3B.
Therefore, while the reflected light from the recording surface is transmitted through the beam shaping rising prism 21, a part of the laser light is lost from the returned light due to external / internal reflection, but as is clear from FIG. The components to be lost are many S components having a large reflectance as compared with the P-polarized components, and the dissipation of P-polarized light can be made almost negligible.

Then, the tilt angle of the polarization plane in the returning light returning to the fixed portion becomes the angle: θ'from the angle: θ in FIG. 4 (c) (the initial state reflected on the recording surface), which is apparent. Since the polarization plane rotation angle increases, the S / N ratio of the reproduction signal increases.

An embodiment of claim 2 will be described below.

Ideally, the laser light flux irradiating the recording surface of the optical information recording medium should be incident so as to be orthogonal to the recording surface. However, in reality, due to warpage of the optical information recording medium, mechanical error of the driving device, and the like. As shown in FIG. 5, a so-called tilt occurs in which the recording surface is inclined by a small angle from the direction orthogonal to the optical axis of the irradiation laser beam. This tilt gives an offset error to the signal detected by the signal detection system, and in particular, an error occurs in the tracking error signal. Therefore, in the beam shaping rising prism of the second aspect, this problem is dealt with as follows.

In FIG. 5A, reference numeral 25 indicates a two-divided light receiving element. Since the incident surface 211 of the beam shaping rising prism 21 has a finite incident angle with respect to the returning light, a part of the returning light is internally reflected by the incident surface 211. Since the direction of this reflected light changes according to the tilt amount when the recording surface 31 has a tilt, a two-divided light receiving element 25 as shown in FIG. 5B is provided at a position where the reflected light can be received. Fix it. The dividing line of the light receiving portion of the two-divided light receiving element 25 is oriented orthogonal to the displacement direction of the reflected light flux due to the tilt as shown in FIG. 5B, so that the outputs from the respective light receiving portions are equal when there is no tilt. Adjust the deployment position. By doing so, the tilt amount can be detected by the output of the two-divided light receiving element, so that the offset error of the detection signal by the signal detection system can be corrected by the detected tilt amount.

The beam shaping rising prism according to the second aspect can be applied to any of the embodiments described with reference to FIGS.

Next, an embodiment of the invention of claim 4 will be described.

As described above, the displacement direction of the movable part is the direction of the laser beam from the fixed part, but this is an ideal case, and in reality, the direction of the laser beam from the fixed part and the direction of the movable part. There is a slight deviation from the moving direction due to mechanical error. This "deviation" also causes an error particularly with respect to the tracking error signal unless it is corrected by some method. In the device of claim 3, this problem is dealt with as follows.

That is, in FIG. 5A, reference numeral 27 is a two-divided light receiving element. The two-divided light receiving element 27 is fixedly arranged on a stationary member (not shown) in the movable portion. The laser light flux from the fixed portion side should ideally enter the entrance surface 211 of the beam shaping rising prism as shown by the solid line in the figure, but in reality, the moving direction of the movable portion due to mechanical error and the laser light flux Due to the "shift" from the direction, the laser light flux enters as shown by the broken line. Therefore, the two-divided light receiving element 27 as shown in FIG.
To receive light. The light receiving portion dividing line of the two-divided light receiving element is oriented in a direction orthogonal to the displacement direction of the reflected light flux due to the above "deviation", and the outputs from the respective light receiving portions are made equal when there is no "deviation". In this way, since the "deviation" in the moving direction of the laser beam from the fixed part and the movable part can be detected by the output of the two-divided light receiving element 27, the error of the tracking error signal based on this "deviation" can be properly corrected. .. Note that the "deviation" includes a deviation in a direction orthogonal to the drawing in FIG. 5A, but since the deviation in this direction is substantially parallel to the track direction, the influence on the tracking error signal is not considered. good.

[0034]

As described above, according to the present invention, a novel beam shaping rising prism and an optical information recording / reproducing apparatus using the same can be provided. The beam shaping rising prism of claims 1 and 2 has a function of raising the laser light flux from the fixed portion toward the recording surface of the optical information recording medium, and a function of shaping the cross-sectional shape of the light flux of the laser light flux. ..
Therefore, by using this, the dedicated beam shaping prism conventionally used can be omitted on the fixed part side of the optical information recording / reproducing apparatus (claims 3, 4, 5), and the fixed part can be effectively used. Can be made compact. Claim 2
The effect of tilt can be effectively eliminated by using the beam shaping start-up prism. According to the apparatus of claim 4, the influence of the error in the moving direction of the movable portion can be effectively corrected. Further, in the apparatus of claim 5, it is possible to reproduce the magneto-optically recorded information with a high S / N ratio.

Further, the optical information recording / reproducing apparatus of the third to fifth aspects can be implemented as a write-once type or a rewritable type.

[Brief description of drawings]

FIG. 1 is a diagram for explaining one embodiment of an optical information recording / reproducing apparatus of the present invention.

FIG. 2 is a diagram for explaining the principle of beam shaping in the present invention.

FIG. 3 is a diagram for explaining a feature of the invention of claim 5;

FIG. 4 is a diagram for explaining a characteristic part of the invention of claim 5;

FIG. 5 is a diagram for explaining a characteristic part of the beam shaping rising prism of claim 2 and the optical information recording / reproducing apparatus of claim 4;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Fixed part 11 LD light source 13 Collimating lens 20 Movable part 21 Beam shaping rising prism 23 Objective lens 30 Optical disk as an optical information recording medium 211 Incident surface 212
Reflective surface 213 Exit surface

Claims (5)

[Claims] 1. A fixed part fixed at a fixed position, comprising an LD light source part for emitting a laser beam and a detecting means for detecting the information contained in the return light from the optical information recording medium, and an optical information recording medium. In the optical information recording / reproducing apparatus, which is movable in the track arrangement direction and has a movable portion that converges the laser light flux from the fixed portion as a spot on the recording surface of the optical information recording medium. A prism for shaping the cross-sectional shape of the laser light flux in order to raise the laser light flux from the fixed portion toward the recording surface and to make the shape of the spot focused on the recording surface into a desired shape, The incident surface on which the laser light flux from the fixed portion is incident, the reflecting surface that internally reflects the laser light flux incident from this incident surface, and the laser light flux reflected by the reflecting surface are recorded on the optical information recording medium. Has an exit surface for exiting toward the body, and by refraction at the entrance surface and / or the exit surface,
A beam shaping rising prism, which shapes the cross-sectional shape of a light beam emitted from the exit surface into a desired shape. 2. A two-divided light receiving element for detecting the tilt of the optical information recording medium by receiving the internally reflected light flux from the incident surface of the return light from the optical information recording medium according to claim 1. Beam shaping startup prism. 3. An optical information recording / reproducing apparatus having a beam shaping rising prism according to claim 1 or 2 in a movable portion. 4. The laser light flux from the fixed portion according to claim 3, wherein a component of the laser light flux from the fixed portion, which is externally reflected by the incident surface of the beam shaping rising prism, is received. An optical information recording / reproducing apparatus, characterized in that the movable portion has a light receiving means for detecting a shift in the direction of the. 5. The optical information recording medium according to claim 3 or 4, wherein the optical information recording medium is a magneto-optical recording medium, and the direction of S polarization of the laser beam from the fixed portion is parallel to the incident surface of the beam shaping rising prism. And an optical information recording / reproducing apparatus for reproducing optical information on the optical information recording medium by utilizing the magneto-optical Kerr effect.