JPH0652582B2 - Optical head - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical head used in an optical information recording / reproducing apparatus and the like, and particularly records a signal on an information recording disk (hereinafter referred to as an optical disk). However, the present invention relates to an optical head suitable for reproducing and erasing the recorded signal.

[Conventional technology]

In the conventional erasable optical head, when erasing the signal recorded on the optical disk, it is necessary to make the spot diameter of the erasing optical spot sufficiently larger than the recording pit width in order to prevent the unerased portion. is there. However, if a desired optical system is provided in the optical head in order to realize this, there is a problem that the number of parts of the optical head increases.

Then, for such a problem, for example, Japanese Patent Laid-Open No. 61-61
In JP-A-206926, a semiconductor laser array having two independent light emitting points at extremely close positions is used as a light source, and two light beams from the semiconductor laser array are provided at two substantially the same positions on a recording track. This semiconductor laser array is arranged as an optical spot so as to be irradiated side by side in the radial direction of the optical disk. When recording or reproducing, only one light beam is turned on for recording or reproducing, and when erasing, two laser beams are recorded. There is described a configuration in which the recording pits are erased at a width equal to or larger than the width of the recording pit row by simultaneously turning on the light beams.

[Problems to be solved by the invention]

However, in the above-mentioned proposed example, it is necessary to irradiate two independent light beams to almost the same position on the same recording track, and there is a big problem in adjusting the position and securing stability, and at the time of recording or reproducing. Since the recording / reproducing light beam is irradiated to the recording pit with a slight deviation, there is a problem when the recording / reproducing performance is deteriorated.

By the way, in recent years, there is a demand for immediate rewriting in which signal recording and erasing are performed at substantially the same time. However, in order to do this, the recording light beam and the erasing light beam are positioned so that the recording light beam optical spot and the erasing light beam optical spot are simultaneously located on the same recording track of the optical disc. The erasing light beam and the erasing light beam must be generated separately from each other so that the intensity can be independently modulated. (In general, the light source for generating the recording light beam is also the light source for generating the reproducing light beam. , Is shared with recording and playback.). For this reason, conventionally, an erasable optical head has generally been configured to mount two or more semiconductor laser light sources. However, in such a structure, there is a problem that the optical head becomes large in size and complicated.

In the above-mentioned proposed example, when erasing, two light beams must be turned on at the same time, so that a signal cannot be recorded almost at the same time as erasing, so that the above-mentioned immediate rewriting is not possible. It was possible.

The object of the present invention is to solve the above-mentioned problems of the prior art,
With a simple structure, the spot diameter of the erasing optical spot is made sufficiently larger than the recording bit to prevent unerased signals.
At the same time, it is to provide an optical head capable of immediately rewriting a signal.

[Means for solving problems]

In order to achieve the above object, in the present invention, as a light source,
While using a semiconductor laser light source in which two semiconductor laser light emitting elements which emit light beams of mutually different wavelengths are closely arranged and fixed on the same plate, for example, a light beam of one wavelength is transmitted and the other one is transmitted. A light beam of a wavelength is reflected by a mirror surface having wavelength selectivity, and a space filter having an opening whose length corresponding to the radial direction of the optical disk is smaller than the opening diameter of the objective lens is provided at the center of the semiconductor. It was arranged in the optical path between the laser light source and the objective lens.

[Action]

The two semiconductor laser light emitting elements are arranged on the same flat plate and are opposed to each other with a distance of about several tens of μm, and are fixed via a base, respectively, and can be independently turned on. . Therefore, the recording / reproducing optical spots and the erasing spots can be independently irradiated to the adjacent positions on the same recording track of the optical disk with a structure substantially similar to that of the conventional one-laser light head. It is possible to rewrite immediately.

Further, among the light beams incident on the space filter from the semiconductor laser light source, the recording / reproducing light beam is transmitted and the erasing light beam is reflected on the mirror surface, whereby recording / reproducing is performed. The light beam passes through the entire space filter, but the erasing light beam only passes through the space filter. Therefore,
Only the luminous flux diameter of the erasing light beam can be selectively made smaller than the aperture diameter of the objective lens.

By the way, when the light beam diameter of the light beam incident on the objective lens is smaller than the aperture diameter of the objective lens, the spot diameter of the light spot irradiated on the optical disk is inversely proportional to the light beam diameter of the light beam. Therefore, as described above, by selectively reducing only the luminous flux diameter of the erasing light beam by the space filter, the erasing light spot becomes inversely proportional to it and becomes sufficiently larger than the recording pit width. It is possible to prevent the unerased residue.

〔Example〕

 The first embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a sectional view schematically showing the structure of an optical head as a first embodiment of the present invention. Also, FIG. 1A shows the first
It is a principal part enlarged view of the optical disk surface in the figure.

In FIG. 1, 1 is a semiconductor laser light source, 2 is a collimating lens, 3 is a polarization beam splitter (hereinafter referred to as PBS), 4 is a quarter wavelength plate, 5 is an objective lens, 6 is an optical disc, and 7 Is a Fuco prism, 8 is a detection lens, 9 is a multi-segment photodetector, and 40 is a spatial filter. Also,
In FIG. 1A, the arrow v indicates the rotation direction of the optical disk 6.

FIG. 2 is a perspective view showing the semiconductor laser light source in FIG. 1 with a part thereof cut away.

As shown in FIG. 2, the semiconductor laser light source 1 includes two semiconductor laser light emitting elements 1a and 1b and bases 1c and 1d, which independently emit laser beams having different wavelengths, in the same housing 1e. They are arranged facing each other. With such a facing arrangement, the semiconductor laser light emitting devices 1d and 1b are
The distance t between the light emitting points can be set to about several tens of μm.

As shown in FIG. ₁ , the recording / reproducing light beam 31 (solid line) of the wavelength λ ₁ generated from the semiconductor laser light source 1 and the wavelength λ ₂
The erasing light beam 32 (broken line) is at least λ
After being converted into a parallel light beam by the collimating lens 2 whose chromatic aberration has been corrected with respect to the light of wavelengths ₁ and λ ₂ ,
Reach the space filter 40.

FIG. 3 is a perspective view showing the structure of the space filter 40 in FIG. 1, and FIG. 4 is a graph showing the wavelength dependence of the reflectance of the wavelength selective mirror surface 41 forming the space filter 40 in FIG. ,.

As shown in FIG. 3, the spatial filter 40 has a reflectance of about 0% at the wavelength λ ₁ of the recording / reproducing light beam 31 as shown in FIG. 4, and a reflectance of about 100% at the wavelength λ ₂ of the erasing light beam 32. And a circular opening 42 provided substantially in the center thereof. Opening diameter D of the circular opening 42
₂ is smaller than the aperture diameter of the objective lens 5.

When the light beams 31 and 32 are incident on such a space filter 40, the recording / reproducing light beam 31 having the wavelength λ ₁ is transmitted through the wavelength selective mirror surface 41 as it is, and thus the light beam after passing through the space filter 40 is transmitted. The luminous flux diameter D _{1 of} 31 is exactly the same as before the incidence. On the other hand, the erasing light beam 32 having the wavelength λ ₂ is reflected by the wavelength selective mirror surface 41, so that the circular aperture 42 passes through the space filter 40.
It is only the light flux that is incident on. Therefore, the beam diameter of the erasing light beam 32 after passing through the space filter 40 is reduced to D ₂ .

Next, the light beams 31, 32 that have passed through the space filter 40
Is narrowed down by the objective lens 5 through the PBS 3/4 wavelength plate 4 and, as shown in FIG. 1A, at the positions close to each other on the recording track 6a of the optical disk 6, the recording / reproducing light is reproduced. A spot 21 and an erasing light spot 22 are formed respectively.

Furthermore, each light beam reflected by the optical disk 6 is again
After passing through the objective lens 5 and the quarter-wave plate 4 and reflected by the PBS 3, the light enters the photodetection system including the Fuco prism 7, the detection lens 8 and the multi-divided photodetector 9, and the recording signal, the focus, and the tracking. Each servo signal is detected. Since this detection system is not directly related to the present invention, detailed description thereof will be omitted.

By the way, between the light spot diameter d narrowed down on the optical disk 6 by the objective lens 5 and the light flux diameter D of the light beam forming the light spot, the light flux diameter D is smaller than the aperture diameter of the objective lens 5. If is also small, the following equation holds.

d≈2 · k · λ · f / D (1) where λ: wavelength of the light beam f: focal length of the objective lens 5 k: proportional constant As is clear from the equation (1), the spot diameter d Is inversely proportional to the beam diameter D of the light beam incident on the objective lens 5. That is, as the luminous flux diameter D of the light beam incident on the objective lens 5 is reduced, a larger spot diameter d is obtained.

FIG. 5 is an explanatory diagram for explaining the relationship between the light beam diameters of the light beams 31 and 32 incident on the objective lens 5 in FIG. 1 and the spot diameters of the light spots 21 and 22.

That is, according to the present embodiment, as described above, the beam diameter of the erasing light beam 32 is set to the aperture diameter D _{2 of the} circular opening 42 by the space filter 40, as shown in FIG. Since the diameter is reduced to the same value, the spot diameter d of the erasing light spot 22 is set by setting the aperture diameter D ₂ to an appropriate size.
_As shown in FIG. 5 (b), ₂ can be made sufficiently wider than the pitch width of the recording pit recorded on the recording track 6a. Therefore, the unerased signal can be sufficiently prevented.

FIG. 6 is an explanatory diagram for explaining the relationship between the light beam diameters of the light beams 31, 32 and the spot diameters of the light spots 21, 22 when the shape of the opening 42 of the space filter 40 is different from that of FIG. .

As shown in FIG. 6 (a), the opening 4 of the space filter 40.
When 2 is an oval shape and the light beam diameter D ₂ ′ corresponding to the direction of the recording track 6 a is shorter than the light beam diameter D ₂ corresponding to the radial direction of the optical disk 6, the erasing optical spot 22 is at the sixth position.
As shown in FIG. 6B, the optical spots are elongated in the direction of the recording track 6a, and the erasing performance can be further improved by the gradual heating / cooling effect.

The shape and size of the opening 42 provided in the space filter 40 are not limited, and the erasing optical spot 22 having a desired shape can be obtained by any shape.

Furthermore, according to this embodiment, the recording / reproducing light beam 3 is used.
1 and the erasing light beam 32 are not emitted from two independent semiconductor laser light sources as in the prior art, but as shown in FIG. 2, they are adjacent to each other on the same flat plate in the same casing 1e. The semiconductor laser light source 1 is composed of two semiconductor laser light emitting elements 1a and 1b arranged and fixed, and is then irradiated onto the optical disk 6 through the same optical system. There is an advantage that it is possible to prevent the optical spots 21 and 22 from being displaced relative to each other due to the influence of vibration and the like, and to obtain high irradiation position stability.

FIG. 7 is a sectional view schematically showing the constitution of the second embodiment of the present invention.

In FIG. 7, the same components as those in the embodiment of FIG. 1 are designated by the same reference numerals.

In the present embodiment, the space filter 40 including the wavelength selective mirror surface 41 and the opening 42, as shown in FIG.
It is formed on the light beam incident surface of S3. By thus combining the space filter 40 and other optical components, the number of optical components can be reduced.

FIG. 8 is a sectional view schematically showing the construction of the third embodiment of the present invention.

In FIG. 8, the same components as those of the embodiment shown in FIGS. 1 and 7 are designated by the same reference numerals.

In this embodiment, as shown in FIG.
Is fixed to the holder 10 together with the objective lens 5 and integrated.

That is, according to the output signal of the photodetector 9, the signal processing circuit 11
Then, the focus actuator 12 and the tracking actuator 13 are controlled, whereby the holder 10, the objective lens 5 fixed to the holder 10 and the space filter 40 are integrated to form an optical axis. Direction (z-axis direction) and tracking direction (x-axis direction),
Focus control and tracking control are performed.

As described above, by integrally driving the objective lens 5 and the space filter 40, the relative position between the opening 42 of the space filter 40 and the objective lens 5 can be fixed, so that the erasing light beam due to the movement of the objective lens 5 can be fixed. It is possible to eliminate the change in the vignetting amount of 32 (the amount of light of the erasing light beam 32 emitted from the space filter 40 that is not incident on the objective lens 5).

As in the above embodiments, the space filter 40 can be arranged in any optical path from the semiconductor laser light source 1 to the objective lens 5, and can be combined with other optical components.

FIG. 9 is a sectional view schematically showing the construction of the fourth embodiment of the present invention.

In FIG. 9, the same components as those of the above-described embodiment are designated by the same reference numerals.

In this embodiment, as shown in FIG. 9, the space filter 40
Are arranged so as to be inclined with respect to the light beams 31 and 32, and the erasing light beam 32 that reflects the space filter 40.
However, the structure is such that it does not return to the semiconductor laser light source 1.
With such a configuration, it is possible to prevent the generation of laser noise due to the returning light.

As described above, the space filter 40 may be inclined with respect to the light beams 31 and 32 at an arbitrary angle. However, at this time, the wavelength selectivity of the wavelength selective mirror surface 41 changes depending on the incident angle of the light beam, so that the film design is performed so that a desired wavelength selectivity is obtained for the light beam of a predetermined incident angle. Need to do. The shape of the opening 42 also needs to be designed so that the erasing light spot has a desired shape.

FIG. 10 is a sectional view schematically showing the constitution of the fifth embodiment of the present invention. Further, FIG. 10A is an enlarged view of a main part of the optical disc surface in FIG.

In FIG. 10, the same components as those in the above-described embodiment are designated by the same reference numerals.

In the present embodiment, the reflected light beam from the optical disk 6 reflected by the PBS 3 has its optical path bent by the optical path changing mirror 14 and then reaches the photodetection system.

Further, in this embodiment, the raising mirror 15 and the space filter 40 are combined. That is, as shown in FIG. 11, a space filter 40 including a wavelength selective mirror surface 41 and a circular opening 42 is formed on the reflection surface of the rising mirror 15. Moreover, as shown in the figure, the wavelength-selective mirror surface 41 is y with respect to the reflection surface of the rising mirror 15.
It is provided so as to be slightly inclined in the z plane.

Therefore, of the recording / reproducing light beam 31 and the erasing light beam 32 that have entered the space filter 40, the total light flux of the light beam 31 and the central portion 32a of the light beam 32 that has entered the opening 42 of the space filter 40 are The light passes through the space filter 40 and is reflected by the reflection surface of the rising mirror 15. On the other hand, the outer peripheral portion 32 b of the light beam 32 that has entered the wavelength selective mirror surface 41 of the spatial filter 40 is reflected by the wavelength selective mirror surface 41. At this time, since the wavelength-selective mirror surface 41 is slightly inclined with respect to the reflection surface of the rising mirror 15, the light beam 32b is in the circumferential direction (y-axis direction) of the optical disk with respect to the light beams 31 and 32a. It is reflected with a slight tilt.

As a result, on the recording track 6a of the optical disk 6, as shown in FIG. 12, the recording / reproducing light spot 21 formed from the recording / reproducing light beam 31 and the erasing light beam 32a are formed. The erasing light spot 22a having a large spot diameter and the erasing light beam 32 adjacent thereto.
The light spots 22b formed of b and having a small spot diameter and a large strength of the surrounding annular portion are respectively irradiated. Therefore, at the time of erasing, this erasing optical spot 22a
And 22b both irradiate the recording track 6a with a strong light intensity, and the erasing is performed by the effect of temperature rising and slow cooling.

By adopting the configuration as in this embodiment, it is possible to eliminate the light amount loss of the erasing light beam and perform the erasing efficiently.

FIG. 13 is a sectional view schematically showing the constitution of the sixth embodiment of the present invention.

In FIG. 13, the same components as those of the above-described embodiment are designated by the same reference numerals.

In this embodiment, the space filter 40 'is composed of a wavelength selective mirror surface 43 and a total reflection mirror surface 44 as shown in FIG. The wavelength-selective mirror surface 43 has a high reflectance at the wavelength λ ₁ of the recording / reproducing light beam 31 and a wavelength λ ₂ of the erasing light beam 32, as shown in FIG. The reflectance is getting low.

Therefore, by using the spatial filter 40 ', the recording / reproducing light beam 31 reflects the entire light flux, and the erasing light beam 32 reflects only the central portion of the light flux incident on the total reflection mirror surface 44. Therefore, by setting the area of the total reflection mirror surface 44 to an appropriate size, the luminous flux diameter of the erasing light beam 32 can be reduced to an arbitrary diameter, and as a result, the spot diameter of the erasing light spot 22 is enlarged. be able to.

In this way, by using the spatial filter 40 of the reflection type, the beam diameter of the erasing light beam 32 can be reduced while bending the optical path. Therefore, it is possible to use the space filter 40 as a stand-up mirror and a mirror for changing the optical path.
The number of parts can be reduced.

〔The invention's effect〕

According to the present invention, the spot diameter of the erasing light spot can be made sufficiently larger than that of the recording pit, and the unerased signal can be prevented with a structure substantially similar to that of the conventional one-laser light head dedicated to recording. It is also possible to rewrite the signal immediately.

Further, the recording / reproducing light beam and the erasing light beam are emitted from one semiconductor laser light source composed of two or more semiconductor laser light emitting elements which are fixedly arranged close to each other on the same flat plate, and have the same optical system. Since the light is radiated onto the optical disk after passing through, the relative positional deviation of each optical spot caused by the influence of heat, vibration, etc. can be suppressed, and high irradiation position stability can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing the constitution of the first embodiment of the present invention, FIG. 1A is an enlarged view of a main part of an optical disk surface in FIG. 1, and FIG. 2 is a semiconductor laser in FIG. FIG. 3 is a perspective view showing a light source partially broken, FIG. 3 is a perspective view showing the structure of the spatial filter in FIG. 1, and FIG. 4 is a wavelength dependence of the reflectance of the wavelength selective mirror surface in FIG. The graph shown in FIG. 5 is an explanatory view for explaining the relationship between the light beam diameter of each light beam incident on the objective lens in FIG. 1 and the spot diameter of the light spot, and FIG. 6 shows the shape of the opening of the space filter. FIG. 7 is an explanatory view for explaining the relationship between the light beam diameter of each light beam and the spot diameter of the light spot when it is different from FIG. 5, and FIG. 7 is a schematic diagram of the configuration of the second embodiment of the present invention. FIG. 8 is a sectional view, and FIG. 8 is a sectional view schematically showing the configuration of the third embodiment of the present invention. 9 FIG fourth cross-sectional view schematically showing the structure of an embodiment of the present invention, the fifth Fig. 10 present invention
10A is a cross-sectional view schematically showing the construction of the embodiment of FIG. 10, FIG. 10A is an enlarged view of a main part of the optical disc surface in FIG. 10, and FIG. 11 is a perspective view showing the construction of the raising mirror and the space filter in FIG. FIGS. 12 and 13 are explanatory views showing the light intensity on the recording track 6a in FIG. 10A, FIG. 13 is a sectional view schematically showing the constitution of the sixth embodiment of the present invention, and FIG. FIG. 13 is a perspective view showing the structure of the space filter, and FIG. 15 is a graph showing the wavelength dependence of the reflectance of the wavelength selective mirror surface in FIG. DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser light source, 1a, 1b ... Semiconductor laser light emitting element, 3 ... Polarization beam splitter, 5 ... Objective lens, 6 ... Optical disk, 21 ... Recording / reproducing optical spot, 22 ... erasing light spot, 31 ... recording / reproducing light beam, 32 ... erasing light beam, 40, 40 '...
... Space filters, 41, 43 ... Wavelength selective mirror surface,
42 ... Aperture, 44 ... Total reflection mirror surface.

Claims (5)

[Claims] 1. An optical head for optically recording a signal on an information recording disk and optically reproducing and erasing the recorded signal, and a first light beam for recording / reproducing having different wavelengths from each other. A semiconductor laser light source in which at least two semiconductor laser light emitting elements for respectively generating a second light beam for erasing are closely arranged on the same plate and fixed, and generated from each of the semiconductor laser light emitting elements. From the information recording disk of the irradiated first and second light beams, an objective lens for irradiating the first and second light beams as two light spots at positions close to each other on the information recording disk. At least a reflected light of the first light beam of the reflected light of the above is separated from an optical path connecting the semiconductor laser light source and the information recording disk, and at least In addition, the first light beam is transmitted (or reflected) and the second light beam is reflected (or transmitted), and the first and second light beams are transmitted to approximately the center of the mirror surface having wavelength selectivity. (Or reflected), a space filter having a region having a length corresponding to at least the radial direction of the information recording disk smaller than the aperture diameter of the objective lens is provided between the semiconductor laser light source and the objective lens. Of the first and second light beams incident on the space filter from the semiconductor laser light source provided in the optical path, at least a light beam transmitted (or reflected) through the space filter is incident on the objective lens. An optical head characterized by being placed. 2. The optical head according to claim 1, wherein at least two semiconductor laser light emitting elements for respectively generating the first and second light beams in the semiconductor laser light source are first and first. The first and second semiconductor laser light-emitting elements are arranged on the flat plate such that the perpendicular lines standing on their joint surfaces are substantially the same and the first and second semiconductor laser light-emitting elements are the same. With the first and second bases on which the semiconductor laser light emitting elements are respectively arranged,
An optical head, which is arranged and fixed so as to face each other at a position substantially symmetrical with respect to a predetermined reference plane parallel to the optical axes of the first and second light beams. 3. The optical head according to claim 1, wherein the space filter is a predetermined one of the light beam separating means arranged in an optical path between the semiconductor laser light source and the objective lens. An optical head arranged on an optical surface. 4. The optical head according to claim 1, wherein at least the space filter is driven integrally with the objective lens when the objective lens is driven by tracking control. A light head characterized by that. 5. The optical head according to claim 1, wherein the space filter is a reflection mirror of an optical path changing total reflection mirror arranged in an optical path between the semiconductor laser light source and the objective lens. An optical head, which is arranged on a surface.