JPH01287830A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To reduce the quantity of the positional fluctuations of an optical disk face inside accompanied by the optical path change of a parallel pencil of rays even in case of the change in a wave length being caused on a divergent light with the output of a semiconductor laser being changed by forming a beam shaping means by using a nitrate material of a low dispersion. CONSTITUTION:The divergent light emitted from a semiconductor laser 1 is made a parallel light by a collimator lens 2, converted into an almost circular sectional parallel light by a beam shaping means 3 and an optical spot is formed by an objective lens 5 on an optical disk 6. The reflected light from the optical disk 6 is separated by a light flux separating means 8 and received by the information signal detecting means 12, 13 detecting an information signal and the servo signal detecting means 11, 12 detecting the servo signal. Now the beam shaping means 3 is formed by using a nitrate material of a low dispersion. Even in case of a wavelength variation being caused on a divergent light with the output of the semiconductor laser 1 being changed, the positional fluctuation of the optical disk face 6 inside accompanied by the light path change of a parallel light flux and a defocusing amt. can be reduced for the optical spot formed on the optical disk 6.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical recording and reproducing apparatus that uses a magnetic thin film as a recording medium and records, reproduces, and erases information by irradiating the recording medium with a light beam such as a laser beam. It is something.

2. Description of the Related Art An example of a schematic configuration of a conventional optical recording/reproducing apparatus is shown in FIG.

In FIG. 2, 1 is a semiconductor laser, 2 is a collimating lens, 3 is a beam shaping prism which is a beam shaping means, and 4 is a beam shaping prism.
A half mirror 15, which is a beam separating means, is an objective lens and forms a light condensing section. 6 is an optical disk which is a recording medium, 7 is a 1/2 wavelength plate, 8 is a polarizing beam splitter,
9 and 10 are convex lenses, 11 is a focus error detector, 1
2.13 is a photodetector. In this configuration, the convex lens 9
．． Focus error detector 11. The photodetector 12 serves as a focus error detection means, and the convex lens 10. The photodetector 13 forms tracking error detection means.

Note that this conventional example shows a so-called magneto-optical recording and reproducing device among optical recording and reproducing devices.

Further, the beam shaping prism 3 is formed using (B K 7 ), which is the most common engineering glass.

The operation of the conventional optical recording/reproducing device will be described below with reference to the drawings.

Divergent light from the semiconductor laser 1 passes through a collimating lens 2 to become parallel light, and passes through a beam shaping prism 3 to become a beam with a substantially circular cross section. This beam passes through the half mirror 4, passes through the objective lens 5, and forms a light spot on the optical disk 6.

The reflected light from the optical disk 6 passes through the objective lens 5 and is reflected and transmitted by the half mirror 4. The reflected light passes through a 1/2 wavelength plate 7 and is split by a polarizing beam splitter 8, which is an analyzer, and each is focused by a lens 9°IO and enters a photodetector 12.13.

Regarding information detection, since the plane of polarization of the reflected light of the linearly polarized semiconductor laser beam irradiated onto the optical disk 6 rotates due to the Kerr effect depending on the direction of magnetization, the output of the photodetector 12 or 13 having the above configuration is changes depending on the direction of magnetization. Furthermore, in order to cancel recording medium noise, etc., a differential detection configuration is adopted with two detectors 12 and 13, and information is reproduced.

Furthermore, regarding error signal detection, a focus error signal is detected by a light beam that is condensed by a convex lens 9, passes through a focus error detector 11, and enters a photodetector 12. Further, the tracking error signal is detected by a light beam that is focused by a convex lens IO and enters the photodetector 13. That is, the photodetector 13 is a two-split photodetector, and if it is set at a position that divides the amount of incident light beam into two,
The tracking error signal can be detected by so-called push-pull detection.

FIG. 3 is a perspective view showing a semiconductor laser and a far-field image of diverging light from the semiconductor laser. In FIG. 3, l is a semiconductor laser.

The semiconductor laser 1 emits light differently in a direction parallel to the semiconductor laser chip bonding surface and in a direction perpendicular to the semiconductor laser chip bonding surface. That is, the far-field image emitted from the semiconductor laser 1 has an elliptical shape.

Therefore, in FIG. 2, the cross-sectional shape of the parallel light that has passed through the collimating lens 2 is an ellipse (cross section A-A). This parallel light enters the beam shaping prism 3, which has a triangular prism shape. The beam is expanded by refracting only the side parallel to the semiconductor laser chip bonding surface of the parallel light, and converted into a beam with a substantially circular cross section (cross section B-B).

Problems to be Solved by the Invention In the conventional optical recording/reproducing device described above, since the beam shaping prism 3 is formed using the most common optical glass (BK7) as a glass material, the refractive index fluctuation of the glass material (BK7) = "Refractive index change with respect to wavelength change" cannot be ignored.

That is, when the output of the semiconductor laser l changes and the wavelength of the diverging light changes, the optical path of the parallel light beam changes from the optical path at the time of initial design.

This optical path change will be described in detail. The glass material (BK7) has a refractive index at a wavelength of 830 nm; n = 1.5097
4. Refractive index variation: m#-1,8XIO'5/nm. Using this refractive index n = 1.50974, the apex angle is determined so that the beam is perpendicularly incident on the half mirror 4, and the beam shaping prism 3 and the optical path of the parallel beam are initially designed.

Here, if the output of the semiconductor laser l changes and a wavelength change of C=10 nm occurs in the diverging light, the refractive index of the beam shaping prism 3 changes to n=1.50956.

At this time, the light emitted from the beam shaping prism 3 passes through an optical path different from the initial design, and enters the half mirror 4 at an angle instead of perpendicularly. This optical path change causes the position of the light spot formed on the optical disc 6 to vary within the surface of the optical disc 6, so that stable recording, reproduction, and erasing cannot be realized.

In view of the above-mentioned problems, the present invention makes it possible to reduce the light spot formed on the optical disk by simply using a low-dispersion glass material even when the output of the semiconductor laser 1 changes and the wavelength of the diverging light changes. Therefore, positional fluctuations within the optical disk surface due to changes in the optical path of the parallel light beam can be reduced. therefore,
An object of the present invention is to provide an optical recording and reproducing device that can always realize stable recording, reproducing, and erasing.

Means for Solving the Problems To achieve this object, the optical recording and reproducing apparatus of the present invention comprises:
An optical disk as a recording medium, a semiconductor laser as a light source, a collimating lens that converts the diverging light from the semiconductor laser into parallel light, and the parallel light from the collimating lens enters and transforms the elliptical cross-section parallel light into approximately circular cross-section parallel light. an objective lens that converts the parallel light from the beam shaping means into a light spot on the optical disk; a beam separating means that separates the reflected light from the optical disk; and a beam separating means that separates the light beam separated by the beam separating means. The beam shaping device is characterized by comprising information signal detection means for detecting an information signal when the beam is incident, and servo signal detection means for detecting a servo signal, and the beam shaping means is formed using a dispersion glass material. .

Effect With this configuration, even if the output of the semiconductor laser changes and the wavelength of the diverging light changes, just by using a low-dispersion glass, the light spot formed on the optical disk will be parallel to the light spot. It is possible to reduce the amount of positional fluctuation within the optical disk surface due to changes in the optical path of the light beam.Therefore, stable recording is possible at all times.

Reproduction and erasure can be realized.

EXAMPLE An example of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of an optical recording/reproducing apparatus according to an embodiment of the present invention.

In FIG. 1, 1 is a semiconductor laser, 2 is a collimating lens, 3 is a beam shaping prism which is a beam shaping means,
Reference numeral 4 denotes a beam separating means, and a half mirror 15 is an objective lens and forms a light condensing section. 6 is an optical disk which is a recording medium, 7 is a 1/2 wavelength plate, 8 is a polarizing beam splitter, 9 and 10 are convex lenses, 11 is a focus error detector,
12 and 13 are photodetectors. In this configuration, a convex lens 9, a focus error detector 11. The photodetector 12 serves as a focus error detection means, and the convex lens 10. The photodetector 13 forms tracking error detection means.

The above-mentioned components are exactly the same as those of the conventional example shown in FIG. 2, and represent a so-called magneto-optical recording/reproducing apparatus among optical recording/reproducing apparatuses.

Here, the beam shaping prism 3 is made of a low-dispersion glass material (CaFK95)'Reference: p45-p46. No.8
9. Formed in April 1987 using an Oplus EJ.

The operation of one embodiment of the present invention configured as described above is as follows.
Since the operation is exactly the same as that of the conventional optical recording/reproducing apparatus shown in FIGS.

In the optical recording/reproducing apparatus of this embodiment, the beam shaping prism 3
is a glass material with low refractive index fluctuation (refractive index fluctuation/refractive index change with wavelength change). (CaFK95). Therefore, even if the output of the semiconductor laser 1 changes and the wavelength of the diverging light changes, the change in the optical path from the optical path of the parallel light beam in the initial design is small.

This effect will be explained in detail. Glass material (CaFK95)
has a refractive index for a wavelength of 830 nm at a certain component ratio: n d, 4305. Refractive index variation: m';-1,
0x10 stones/n+w. This refractive index n = 1.43
052, the apex angle is determined so that the beam is perpendicularly incident on the half mirror 4, and the beam shaping prism 3 and the optical path of the parallel beam are initially designed.

Here, when the output of the semiconductor laser 1 changes and a wavelength change of C"lOnm occurs in the diverging light, the refractive index of the beam shaping prism 3 changes to n = 1.43402. At this time, the beam shaping prism The light emitted from the mirror 3 passes through an optical path different from the initial design, and enters the half mirror 4 at an angle instead of perpendicularly.

This optical path change causes the position of the light spot formed on the optical disc 6 to vary within the surface of the optical disc 6, and thus affects stable recording, reproduction, and erasing.

However, in the conventional example shown in Fig. 1, the beam shaping prism 3
Refractive index fluctuation of the glass material (BK7) that formed the
1.8 x 10'/nm, the glass material (C
The refractive index variation of aFK95) is approximately 1/2.

Therefore, the amount of variation in the position of the light spot within the surface of the optical disk 6 due to wavelength change is reduced to about 1/2, and the influence on the recording, reproducing, and erasing characteristics is also reduced to about 1/2.

As described above, according to this embodiment, the beam shaping prism that converts parallel light with an elliptical cross section from the collimating lens into a substantially circular cross section is formed using a glass material (CaFK95) with a certain specific component ratio, so that the semiconductor laser The amount of variation in the position of the optical spot within the optical disc surface due to wavelength changes can be reduced to approximately 1/2 of that of the conventional glass material (BK7).

In this example, in order to compare with the conventional example, a triangular prism-shaped beam shaping prism was used as the beam shaping means, but other beam shaping means, such as a beam shaping means combined with a lens system, can also have a low Glass material with a specific component ratio (CaFK95) that has the characteristic of refractive index fluctuation
Compared to using glass material (BK7), even if the output of the semiconductor laser changes and the wavelength of the diverging light changes, the amount of change in focal length 1 working distance of the lens system is small. The amount of defocus of the light spot on the optical disk is also small, and stable recording, re-reading, and erasing can be achieved similarly to this embodiment.

Here, if we look at recent trends in the development of optical recording/reproducing devices, the capacity, high-speed access, and high-speed rotation are progressing, and margins in the characteristics of optical recording/reproducing devices are becoming a problem. In other words, it can be said that an essential condition for an optical recording/reproducing device is to improve its performance as much as possible. For this reason,
By using a low-dispersion glass material, it is possible to reduce the positional fluctuation within the optical disk surface due to changes in the optical path of the parallel light beam and the amount of defocus for the light spot formed on the optical disk, compared to conventional methods. A somewhat stable record.

The ability to reproduce and erase data has a very large effect.

Effects of the Invention The present invention includes an optical disk as a recording medium, a semiconductor laser as a light source, a collimating lens that converts diverging light from the semiconductor laser into parallel light, and a collimated light from the collimating lens entering the elliptical cross section to be parallel. a beam shaping means for converting light into parallel light with a substantially circular cross section; an objective lens for receiving the parallel light from the beam shaping means to form a light spot on the optical disk; and a beam separating means for separating reflected light from the optical disk; The light beam separated by the light beam separating means is incident on the light beam, and comprises information signal detection means for detecting an information signal and servo signal detection means for detecting a servo signal, and the beam shaping means uses a glass material with low dispersion. Even if the output of the semiconductor laser changes and the wavelength of the diverging light changes, the optical spot can be formed on the optical disk simply by using a low-dispersion glass material. On the other hand, it is possible to reduce the positional fluctuation within the optical disk surface due to the change in the optical path of the parallel light beam and the amount of defocus.

Therefore, it is possible to realize an excellent optical recording and reproducing device that can always realize stable recording, reproducing, and erasing.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an optical recording/reproducing device according to an embodiment of the present invention, FIG. 2 is a schematic diagram of a conventional optical recording/reproducing device, and FIG. 3 is a far-field image of divergent light from a semiconductor laser. FIG. l...Semiconductor laser, 2...Collimating lens, 3...Beam shaping prism, 4...
... Half mirror 15 ... Objective lens, 6
...Optical disk, 7...1/2 wavelength plate, 8...Polarizing beam splinter, 9゜lO...
... Lens, 11 ... Focus error detector, 12.13 ... Photodetector. Name of agent: Patent attorney Toshio Nakao (1 person) Figure 1 f Semiconductor label Figure 2 6 Light Tee

Claims (2)

[Claims] (1) An optical disk as a recording medium, a semiconductor laser as a light source, a collimating lens that converts the diverging light from the semiconductor laser into parallel light, and the parallel light from the collimating lens enters to form parallel light with an elliptical cross section. a beam shaping means for converting into parallel light with a substantially circular cross section; an objective lens for receiving the parallel light from the beam shaping means to form a light spot on the optical disk; and a beam separating means for separating reflected light from the optical disk. , comprising information signal detection means for detecting an information signal and servo signal detection means for detecting a servo signal upon the incidence of the light beam separated by the light beam separation means, and the beam shaping means is configured to detect a dispersion glass material. An optical recording/reproducing device characterized in that it is formed using the above. (2) The optical recording/reproducing apparatus according to claim (1), wherein the low-dispersion glass material is CaFK95.