JP3081307B2 - Optical information recording / reproducing method and device therefor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention is an optical disc TECHNICAL FIELD OF THE INVENTION The light mosquito - de like optical information method records reproduction information in the recording medium and its
Relates to a device, particularly suitable for conducting recording and high-resolution reproduction of the recording laser beam and composed of very small pits with a laser light for reproduction information of a specific wavelength, ultra-high density recording and reproduction capable optical information recording The present invention relates to a reproducing method and an apparatus therefor .

[0002]

2. Description of the Related Art An optical information recording medium such as an optical disk has a recording medium.
In an optical information recording apparatus for recording or reproducing information by irradiating the light, a large-capacity recording apparatus capable of high-density recording is desired. Some of them have already been commercialized as compact disks, laser disks, computer external memories, and the like. This type of external storage device is always required to have a high density of recording, and the method of this high density is to (1) use a laser wavelength as short as possible. Some methods have been proposed, such as (2) providing a mask on an optical disk to block adjacent recording pits (recording information) to suppress interference between adjacent recording information. Regarding this proposal, for example, Technical Digest of Optical Data Streed (Topical Meeting), Vol. 5, (1991), No. 112
Pages 115 to 115 (Lecture No. TuB-3) and 1
Page 16 to 119 (Lecture number TuB-4) [Techni
cal Digest of Optical Data Storage, Vol.5, (199
1), pp. 112-115 / pp. 116-119]. This method is characterized in that an information recording layer made of a plurality of magneto-optical materials is used, and a mask layer for suppressing interference of information from adjacent recording pits is provided in addition to the information recording layer. This is because the information (recording pits) recorded in the portion of the information recording layer where the temperature has risen due to the irradiation of the reproducing light spot appears, so that the interference with the adjacent recording pits is suppressed by the effect of the mask and the optical resolution is reduced. This utilizes the effect that is improved. However, in the above method, the time constant becomes large because the information recording layer is limited to the magneto-optical material and the thermal suppression effect is used. However, there is a problem that the influence of the recording pits after reproduction still remains.

[0003]

As described above, in the prior art, the time constant becomes large because the information recording layer is limited to a magneto-optical material and the effect of thermal suppression is used. There is a problem that the mask is not applied to the recording pits (recording information) after the spot has passed, and the influence of the recording pits after reproduction still remains. In order to solve this problem, the present inventors have previously used a thin film made of a saturable absorber and have a property that when the laser light to be irradiated exceeds a certain threshold value, the thin film becomes transparent. There has been proposed an optical information recording medium in which an optical mask is provided to suppress interference between adjacent recording pits and a recording / reproducing apparatus using the same (Japanese Patent Application No. 3-199084). In this method, as shown in FIG. 2, a thin film layer made of a saturable absorber is provided on the surface of the information recording layer on the side irradiated with the laser beam, and information recorded from the recording layer is read. is there. Using the characteristics of the saturable absorber thin film, information composed of minute pits is recorded on the recording layer by a light pot having a diameter smaller than the light spot of the recording laser to be irradiated, and a minute light having a predetermined light intensity or more is obtained. Since only the recorded information in the area is detected, high-resolution reproduction can be performed. However, this method does not cause any particular problem in a read-only information recording device using a low-output laser beam, but has a problem that heat is generated in a recordable optical information recording device using a high-output laser beam. Was.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the prior art, and utilizes the wavelength dependence of a saturable absorber to use a reproducing laser beam in a wavelength region having a large absorption characteristic during reproduction. An optical information recording / reproducing method capable of performing high-resolution reproduction by performing high-resolution reproduction by using a recording laser beam in a wavelength region having no absorption characteristic during recording to eliminate light loss and heat generation and enabling high-resolution reproduction with high-density recording. An object of the present invention is to provide a recording / reproducing apparatus for implementing the present invention.

[0005]

In order to achieve the above object, in the optical information recording / reproducing method of the present invention, an optical information recording medium provided with at least an information recording layer and a thin film layer comprising a saturable absorber is provided. The method for recording information by irradiating a recording laser beam from the side of the thin film layer composed of the saturable absorber to form minute pits, and reproducing the recorded information by irradiating the reproducing laser beam At the time of recording, high-density recording is performed using a recording laser beam in a wavelength region having no supersaturation absorption characteristic, and at the time of reproduction, high-resolution reproduction is performed using a reproduction laser beam in a wavelength region having a supersaturation absorption characteristic. . By the recording and reproducing method as described above, at the time of recording, high-definition recording can be performed through the thin layer of the saturable absorber without being affected by the saturable absorption characteristic, and the loss of the recording laser light is reduced. In addition, generation of heat can be suppressed. At the time of reproduction, the light spot for reproduction on the recording surface can be narrowed down by the effect of the thin film layer of the saturable absorber, and high-resolution reproduction can be performed by the effect of the optical mask by the saturable absorber. In the optical information recording / reproducing method of the present invention, generally, the wavelength of the recording laser light irradiated at the time of recording is longer than the wavelength of the reproducing laser light irradiated at the time of reproduction. That is, at the time of reproduction, information is reproduced using a short-wavelength laser beam, so that higher-resolution reproduction can be performed. Further, the optical information recording device of the present invention,
An optical information recording medium provided with at least a thin film layer composed of an information recording layer and a saturable absorber is attached to a recording head and an information recording / reproducing apparatus equipped with a reproducing head, and provided on the optical information recording medium. And a means for irradiating a recording laser beam having a wavelength not having a saturable absorption characteristic and a reproducing laser beam having a wavelength having a saturable absorption characteristic from the saturable absorber layer side. As a thin film layer made of a saturable absorber provided in the optical information recording medium of the present invention, for example, nickel phthalocyanine shown in FIG. 3 shows an absorption characteristic in a specific wavelength range and does not show an absorption characteristic in other wavelength ranges. Metal complex compounds of phthalocyanine having properties, such as copper, cobalt, and iron, and thin films of various organic dye compounds or compound semiconductors can also be used. The optical information recording medium using a saturable absorber layer, which was the prior application of the present inventors, has been found to be capable of high-density recording and high-resolution reproduction. Since a high-output laser beam is required, it is not preferable to provide a saturable absorber layer on the laser beam irradiation side of the optical information recording layer because heat is generated. However, for example, as shown in FIG. 3, nickel phthalocyanine [D. Dolp
hin; The Porphyrin Vol.3 Academic Press, NY (197
8)], the saturable absorber has a wavelength region exhibiting absorption characteristics depending on the wavelength and a wavelength region exhibiting no absorption characteristics. Therefore, in the recording / reproducing method of the present invention, the wavelength having no absorption characteristics at the time of recording is used. λ ₁ (for example, 800n
m), and a laser beam having a wavelength λ ₂ (for example, 650 nm) having a supersaturation characteristic is used at the time of reproduction. At the time of recording, the laser beam is not absorbed by the saturable absorber layer. There is little loss of laser light reaching and little heat generation, and the output of the recording laser light is not set unnecessarily large. Also, during playback,
Due to the effect of the saturable absorber layer, the light spot diameter on the recording surface on the information recording layer can be narrowed down, so that high resolution reproduction is possible. In addition, since recording and reproduction are provided with laser beam irradiation means of two different wavelength regions, the written information can be reproduced and checked immediately after that, and has a so-called read-after-write function. An optical information recording device can also be used. In the optical information recording / reproducing method of the present invention, irradiating a minute laser beam spot during reproduction to perform high-resolution reproduction of recorded information is indispensable for performing high-density recording and high-resolution reproduction. The condition is that, in the laser light in the two wavelength regions of recording and reproduction, the wavelength of the laser light at the time of reproduction is selected to be shorter than that at the time of recording, and a thin film made of a saturable absorber corresponding to the wavelength is selected. Ultra high resolution regeneration can be realized by combining them.

[0006]

The operation of the present invention will be described with reference to the case of nickel phthalocyanine shown in FIG. 3 as an example. At the time of recording information, as shown in FIG. 3, a wavelength region that does not exhibit a saturable absorption characteristic, for example, a recording laser beam having a wavelength of 800 nm (λ ₁ ) is used. For example, a reproducing laser beam having a wavelength of 650 nm (λ ₂ ) is used. With this setting, the recording can be performed by passing through the saturable absorber thin film without being affected by the saturable absorption characteristics of the laser light during recording, so that the loss of the laser light is small and the problem of heat generation does not occur. Also, at the time of reproduction, the light spot for reproduction on the information recording surface can be narrowed down by the effect of the saturable absorber thin film,
Due to the optical mask function of the saturable absorber thin film, interference with adjacent recording pits (recorded information) is suppressed, and high-resolution reproduction is possible. Further, at the time of reproduction, a reproduction laser beam having a wavelength shorter than the wavelength of the laser beam at the time of recording can be used, so that higher resolution reproduction can be achieved.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the accompanying drawings. <Embodiment 1> FIG. 1 shows an example of the configuration of an apparatus for implementing the method for recording and reproducing optical information according to the present invention. In the figure, a recording optical head is a recording laser light source 3 having a wavelength λ _1.
The laser beam radiated from w is converted into a collimated light beam by a collimating lens 4w and, if necessary, passed through a beam shaping optical system (not shown).
w, a structure in which a recording laser beam is narrowed on the recording layer 14 by passing through a narrowing lens 8w. And
The reflected light from the recording layer 14 passes through the aperture lens 8w, is reflected by the prism 7w and the polarization beam splitter 5w, and is introduced into a signal detection optical system (not shown). The signal detection optical system includes a light point control signal detection optical system that detects a light point control signal such as a focus shift signal and a track shift signal, and an information signal detection optical system that detects address information or a recorded information signal. ing. Among the light point control signal detection methods, the defocus detection method includes a conventionally known astigmatism method or knife edge method, and the track deviation detection method is a diffracted light operation method (so-called push-pull method). Various methods are conceivable. Then, the light beam incident on the information signal detection optical system is
For example, it is configured such that it is polarized and separated into two light beams by a polarizing prism such as a Wollaston prism, and is received by two light receiving surfaces provided on the photodetector 6w to obtain a focus shift signal and a track shift signal. The signal is obtained from the sum signal of these error signals. On the other hand, the reproducing optical head 2 converts the laser beam emitted from the reproducing laser light source 3r having the wavelength λ ₂ into a parallel light beam by the collimating lens 4r, passes through the beam shaping optical system as necessary, and outputs the polarized beam splitter 5r. , Prism 7r, aperture lens 8
r, the laser beam for reproduction is focused on the recording layer 14. Then, the reflected light from the recording layer 14 is processed by the same information signal detection optical system as in the case of the recording optical head 1 described above, and respective signals are obtained. As the saturable absorber layer 13 of the optical information recording medium used in the present embodiment, an optical disk having a 2,000 ° thick saturable absorber layer formed by spin-coating a solution of nickel phthalocyanine shown in FIG. Is mounted on a disk drive device having a recording optical head and a reproducing optical head mounted thereon, and the wavelength (λ ₁ ) of the recording laser light is 800 nm having no saturable absorption characteristic, and the wavelength of the reproducing laser light is used. (Λ ₂ ) is 650n indicating supersaturated absorption characteristics
Recording and reproduction were carried out using the m-type (λ ₁ ≧ λ ₂ ). As a result, high-density recording and high-resolution reproduction twice or three times that of the conventional recording and reproducing methods could be realized. Further, by setting the wavelength shorter than the wavelength lambda ₁ of the recording laser beam wavelength lambda ₂ of the reproducing laser beam, it was obtained even high resolution reproduction.

Embodiment 2 FIG. 4 shows an example of the configuration of a recording / reproducing head when a recording laser light source and a reproducing laser light source are mounted on one head. In the figure, the wavelength λ
_The laser light emitted from the recording laser light source 3w is converted into a parallel light beam by the collimating lens 4w, and if necessary, passed through a beam shaping optical system (not shown) to narrow the beam splitters 10, 11, the prism 7, and the aperture. The laser beam for recording is narrowed on the recording layer 14 through the lens 8. On the other hand, the laser light emitted from the reproduction laser light source 3r having the wavelength λ ₂ is converted into a parallel light beam by the collimator lens 4r, and a beam shaping optical system (not shown) is used as necessary.
Through the beam splitters 10, 11, the prism 7,
The laser beam for reproduction is narrowed on the recording layer 14 by passing through the narrowing lens 8. Then, the recording layer 14
Is reflected by the beam splitter 11 and further reflected by the polarization beam splitter 5, and is reflected in the first embodiment.
Is introduced into the same signal detection optical system as that of
w, 6r are received by two light receiving surfaces provided,
Light spot control signals such as a focus shift signal and a track shift signal are obtained, and the information signal has a structure that is obtained as a sum signal of them. Using the recording / reproducing head having the above-described configuration, the same optical information recording medium as in the first embodiment was mounted on a disk drive and recording and reproduction were performed. Recording and high resolution reproduction were realized. The advantage of this embodiment is that the structure of the recording / reproducing head can be made compact and manufactured at low cost.

[0009]

According to the present invention, in the recording and reproduction of an optical information recording medium provided with a thin film layer composed of a saturable absorber,
Since recording laser light having a wavelength without supersaturation absorption characteristics is used during recording, it is not necessary to increase the recording laser power because loss and heat generation of the recording laser light are extremely small. Since the reproduction laser beam is used, high-resolution reproduction can be realized by the optical mask function of the thin film layer of the saturable absorber. further,
By setting the wavelength of the reproduction laser light to be shorter than the wavelength of the recording laser light, higher resolution reproduction can be achieved.

[0010]

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of a configuration of a recording optical head and a reproducing optical head exemplified in Embodiment 1 of the present invention.

FIG. 2 is an explanatory diagram showing the principle of high-resolution reproduction of an optical information recording medium having a saturable absorber layer exemplified in Example 1 of the present invention.

FIG. 3 is a graph showing the wavelength dependence of a saturable absorber (nickel phthalocyanine) exemplified in Example 1 of the present invention.

FIG. 4 is a schematic diagram showing an example of the configuration of a recording / reproducing optical head shown in Embodiment 2 of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical head for recording, 2 ... Optical head for reproduction, 3w ... Laser light source for recording, 3r ... Laser light source for reproduction, 4w, 4r ...
Collimating lens, 5, 5w, 5r: polarizing beam splitter, 6w, 6r: photodetector, 7, 7w, 7r: prism, 8, 8w, 8r: aperture lens, 9: optical head for recording / reproducing, 10, 11 ... Beam splitter 12: disk substrate, 13: saturable absorber layer, 14: recording layer, 14n
... Recording pits (recording information), 14k ... Laser light irradiation recording pits, 15 ... Protective film, 16 ... Spindle, 17 ... Light irradiation area, 18 ... Detectable area, 19 ... Center of information recording track

────────────────────────────────────────────────── (5) References JP-A-5-73962 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 7/00-7/013 G11B 7 / 125-7/135

Claims (4)

(57) [Claims] 1. A specific wavelength region exhibits absorption characteristics.
Phthalocyanine gold that does not show absorption characteristics in the outside wavelength range
Using an optical information recording medium provided with a thin film layer containing a genus complex compound, information is recorded using laser light in a wavelength range not exhibiting the above-mentioned absorption characteristics, and using laser light in a wavelength range showing the above-mentioned absorption characteristics. An optical information recording / reproducing method characterized by reproducing information. 2. The optical information recording / reproducing method according to claim 1 , wherein the wavelength of the laser beam used for reproduction is shorter than the wavelength of the laser beam used for recording. 3. In a specific wavelength range, the material exhibits absorption characteristics.
Phthalocyanine gold that does not show absorption characteristics in the outside wavelength range
Using an optical information recording medium provided with a thin film layer containing a genus complex compound , the above-described absorption characteristics of the optical information recording medium during recording.
Recording laser light irradiating means for irradiating laser light in a wavelength range not showing the above, and the above-mentioned absorption to an optical information recording medium during reproduction
An optical information recording / reproducing apparatus, comprising: a reproducing laser light irradiating unit for irradiating a laser beam in a wavelength range showing characteristics . 4. The optical information recording / reproducing apparatus according to claim 3 , wherein said reproducing laser beam irradiating means irradiates a laser beam having a shorter wavelength than a laser beam of said recording laser beam irradiating means. An optical information recording / reproducing apparatus, characterized in that: