JPH1021550A - Optical recording / reproducing method, optical head and optical recording device - Google Patents

Abstract

(57) [Problem] To provide an optical recording / reproducing method capable of performing writing (recording) processing with low power and obtaining a high-intensity reproduction signal, and an optical recording apparatus suitable for the method. SOLUTION: At the time of recording, a CD-R (optical disc) 1
650 nm laser light 2 belonging to a wavelength band having a low reflectance
By using No. 3, sufficient energy for recording can be given to the CD-R even with low-power laser light. On the other hand, at the time of reproduction, a high-intensity reproduction signal can be obtained by using the 780 nm laser beam 24 belonging to the wavelength band of high reflectivity of the CD-R. Therefore, it is possible to provide the optical recording apparatus 10 capable of performing recording processing using a low-power and inexpensive semiconductor laser, and at the same time, it is possible to obtain a reproduction signal having a high S / N ratio, thereby reliably reproducing information at high speed. become.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for recording and reproducing data on and from an optical recording medium such as a digital video disk (DVD) and a compact disk (CD), an optical head and an optical recording apparatus.

[0002]

2. Description of the Related Art With respect to optical disks currently on the market, for example, in a compact disk (CD), information is recorded and reproduced using a laser beam having a wavelength of 780 nm. Further, in a digital video disk (DVD), which is one of optical disks having a higher recording density than a CD, recording and reproducing information using a laser beam having a wavelength of 650 nm or 635 nm is being studied.

[0003]

In order to reproduce the information recorded on these optical disks, the optical disk is irradiated with a laser beam using an optical head, and the information is reproduced from the intensity of the light reflected from the optical disk. A signal is used. Since the higher the intensity of the reproduction signal, the higher the S / N ratio, it is suitable for reproducing an optical recording medium having a high recording density and a large recording capacity on an optical disk. In addition, reading errors can be reduced, so that high-speed operation can be achieved, and further, reproduction errors can be reduced, so that reliability can be increased. In order to obtain such a high-intensity reproduction signal, it is necessary to increase the intensity of the reflected light.

On the other hand, when information is recorded on an optical disk, it is necessary to inject predetermined energy for performing physical processing such as changing the phase of a recording layer. Therefore, high-energy laser light is required. However, if the output of the laser light source required for the recording process is low, the cost of the laser light source and the driving circuit can be reduced, and further, the necessary laser light for the recording process is required. Power consumption can be reduced. In order to improve the efficiency of using the energy of laser light, it is better that the absorptance of laser light is high. Therefore, when recording is performed using laser light, it is desirable that the intensity of light reflected from the optical disk be low.

Therefore, in a conventional optical recording apparatus, a laser beam having a wavelength having an appropriate reflectance is adopted from these viewpoints. When recording, the drive power of the laser diode is increased and high-intensity laser light is applied to physically change the recording layer of the optical disk.
At the time of reproduction, processing such as lowering the driving power of the laser diode and reproducing the recorded information so as not to be destroyed is selected. For this reason, in an optical recording apparatus having a recording function, a high-power laser diode is required so that recording can be performed in a wavelength band where a certain degree of reflectivity can be secured, and large power is consumed when performing recording processing. I have.

Accordingly, it is an object of the present invention to provide an optical recording / reproducing method, an optical head, and an optical recording apparatus capable of performing recording with low power and obtaining a large reproduced signal during reproduction. I have. It is possible to perform recording without using an expensive high-power laser diode.Also, power consumption during recording can be significantly reduced, and at the same time, information having a large recording capacity stored in an optical recording medium can be recorded. It is an object of the present invention to provide a highly reliable optical recording / reproducing method, an optical head and an optical recording device capable of reading data at high speed.

[0007]

Therefore, according to the present invention, instead of using laser beams of the same wavelength for recording and reproduction, light having a wavelength band having a low reflectance and a wavelength band having a high reflectance are used. Using a recording medium, recording is performed using a laser beam of a first wavelength belonging to a wavelength band having a low reflectance, and reproduction is performed using a laser beam of a second wavelength belonging to a wavelength band having a high reflectance. I have to. That is, in the optical recording / reproducing method of recording and reproducing information by irradiating an optical recording medium with a laser beam according to the present invention, a recording step of recording information using a laser beam of a first wavelength; And a reproducing step of reproducing information by using a laser beam having a second wavelength different from the wavelength of the laser beam. Such a process using laser beams having different wavelengths involves a laser light source that emits first and second laser beams having different wavelengths and a combination of the first and second laser beams on the same recording layer of an optical recording medium. This can be performed using an optical head characterized by having an optical system capable of emitting light. And, using this optical head,
It is possible to provide an optical recording apparatus including a recording unit that records information on a recording medium by using a first laser beam and a reproducing unit that reproduces information recorded on a recording medium by using a second laser beam. It is also possible to use a plurality of optical heads for individually irradiating laser beams having different wavelengths, and a first optical head capable of condensing the first laser beam on a recording layer of an optical recording medium and recording information. Also, an optical recording apparatus that performs recording and reproduction using a second optical head that can reproduce information by condensing a second laser light having a different wavelength from the first laser light on the recording layer can be provided.

By using an optical head or an optical recording device capable of irradiating at least two laser beams having different wavelengths, it is possible to irradiate an optical recording medium with a laser beam having a wavelength suitable for each recording and reproducing process. It becomes possible. That is, by selecting a wavelength belonging to a wavelength band where the reflectance of the optical recording medium is low as the first wavelength, it is possible to apply sufficient energy to the optical recording medium to perform recording even with a low-power laser beam. Can be. In addition, by selecting a wavelength belonging to a wavelength band having a high reflectance of the optical recording medium as the second wavelength, a high-intensity reproduction signal can be obtained without affecting recorded information. High-density information can be reliably reproduced at high speed. Therefore, the present invention can provide a highly reliable optical recording / reproducing method and optical recording apparatus. In addition, since the recording process can be performed using a low-power laser beam, an expensive high-power laser diode is not required, and an optical recording device that can record information on an optical recording medium can be provided at low cost. Processing can be performed.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION

[Embodiment 1] An embodiment of the present invention will be described below with reference to the drawings, and the present invention will be further described. FIG. 1 shows a configuration example of an optical recording apparatus according to the present invention. The optical recording device 10 of the present embodiment includes an optical head 20 that performs recording and reproduction by irradiating the optical disc 1 with a laser beam. The optical head 20 can irradiate the optical disc 1 with two laser beams having different wavelengths. It has become. For this reason, the optical head 20 of this embodiment includes a hologram laser unit 21 for writing and a hologram laser unit 2 for reproduction.
2 are housed in the housing 29. Inside the optical head 20, the first laser light 23 and the second laser light 24 emitted from the respective laser units 21 and 22 are collimated by collimator lenses 25 and 26, and are collimated by the dichroic prism 27. The light enters the objective lens 28 through the optical path. Then, the first and second laser beams 23 and 24 are focused on the recording layer 1a of the optical disc 1 by the objective lens 28.

The optical disk 1 to be processed by the optical recording apparatus 10 of this embodiment is a CD-standard optical disk (CD-R) having a writable dye-based recording layer 1a. It is an optical disc with selectivity. That is, the optical disc 1 of the present example shows a very high reflectance of 80 to 90% at a wavelength near 800 nm, while
The reflectance for wavelengths near 00 to 700 nm is 15 to 2
It shows a very low value of 0%. Therefore, when a laser beam having a wavelength of about 800 nm is irradiated, the energy absorbed by the optical disk 1 is very small, and it is possible to obtain high intensity reflected light. On the other hand, when a laser beam having a wavelength near 650 nm is irradiated, the reflectance is low, so that most of the energy of the irradiated laser beam is absorbed by the recording layer 1a.

Therefore, in the optical recording apparatus 10 of the present embodiment, energy can be easily applied to the recording layer 1a and the wavelength is 65 nm.
A red laser of 0 nm is selected as the first laser beam 23 for recording. In addition, the wavelength is 780 n with high reflectivity.
m is selected as the second laser beam 24 for reproduction. For this reason, the first optical head 20 of the present example
Has a wavelength of 650 nm.
Has the function of irradiating the laser light 23 of
It also has a function of receiving the light reflected from the optical disc 1 separately from the laser light emitted using a hologram or the like and generating signals for tracking servo and focusing servo. Further, the second hologram unit 22 has a function of irradiating the laser beam 24 having a wavelength of 780 nm, and separates and receives reflected light similarly to the first hologram unit 21 to perform tracking and focusing servo. It has a function to generate signals. Further, the second hologram unit 22 has a function of generating a reproduction signal reflecting information recorded on the optical disc 1 from light reflected by the optical disc 1 in addition to a servo signal. The tracking and focusing servo signals generated by the first and second hologram units 21 and 22 are supplied from the optical head 20 to a servo control unit 11 in the optical recording device 10, and the optical head 20 is actuated by the actuator 12 using a magnetic field. Fine position control is performed. In the optical head 20 of this example, a coil 31 for tracking and focusing control is provided in a housing 29, and the optical head 20 moves integrally to perform position control. Of course, focusing control or tracking control of only the objective lens 28 may be performed.

In the optical recording apparatus 10 of this embodiment, information to be written (recorded) on the optical disk 1 is supplied from a host such as a computer, and the laser drive power corresponding to the information is supplied from the recording circuit 13 to the optical head 20. It is supplied to the first hologram laser unit 21. And
The first laser beam 23 having a short wavelength of 650 nm is irradiated on the optical disc 1 via the objective lens 28, and information is written. On the other hand, when performing reproduction, power is supplied from the reproduction circuit 14 to the second hologram laser unit 22, and
The second laser light 24 having a relatively long wavelength of 0 nm is applied to the optical disc 1 via the objective lens 28. Further, the reflected light from the optical disk 1 via the objective lens 28
Is received by the hologram laser unit 22, and is converted into a reproduction signal and supplied to the reproduction circuit 14. Reproduction circuit 14
Outputs the information obtained from the reproduction signal, that is, the information recorded on the optical disk 1, to the host. In the optical head 20 of the present example, the first and second laser beams 23 and 24 having different wavelengths can be focused on the recording layer 1a of the same optical disc 1 via the same objective lens 28. Spherical aberration and the like due to the difference in wavelength are corrected by the collimator lenses 24 and 25.

As described above, in the optical recording apparatus 10 of the present embodiment, it is possible to irradiate the optical disc 1 with two laser beams having different wavelengths. Therefore, when performing writing, the recording process can be performed by irradiating the optical disc 1 with the 650 nm laser beam 23 having a low reflectance. The CD-R, which is the optical disk of this example, has a laser beam 23 of 650 nm.
Is about 15%. Therefore, when a semiconductor laser of 5 mW is used for the first hologram laser unit 21, about 1 mW of energy is obtained on the surface of the recording layer 1a of the optical disk, and about 85% of this energy is used for the recording layer 1a. Information is written. On the other hand, in the optical recording apparatus 10 of the present example, when the 780 nm laser beam used for reproduction is used for recording, the reflectance is 9%.
Since it is close to 0%, about 7 mW of energy is required on the surface of the recording layer 1a in order to supply the same level of energy to the recording layer 1a. Therefore, it is necessary to prepare a semiconductor laser of about 35 mW. As described above, according to the present invention, the energy required for recording information can be reduced to about 1/7, and the recording process can be performed using a 1/7 output semiconductor laser. Therefore, a writable optical recording device can be provided at very low cost, and power consumption can be significantly reduced. If a conventional 35 mW semiconductor laser is employed, sufficient energy for recording information on the recording layer 1a can be supplied in 1/7 or less of the time, so that a recording speed of about 8 times speed is provided. Optical recording device can be provided.
Therefore, according to the present invention, it is possible to provide an inexpensive optical recording apparatus suitable for an optical disk having a high recording speed and a high recording density.

On the other hand, reproduction can be performed with the laser beam 24 having a high reflectivity of 780 nm, so that reflected light having sufficiently high intensity can be obtained with low power even during reproduction. Therefore, the recorded information is not affected. Also,
Since a reproduced signal having a high S / N ratio can be obtained by high-intensity reflected light, information can be reliably reproduced at high speed.

[Embodiment 2] FIG. 3 shows an example of a different optical recording apparatus according to the present invention. Optical recording device 1 of this example
0 has two optical heads 20a and 20b. In this example, the optical head 20a is a writing optical head, and has a built-in hologram laser unit 21 for irradiating the above-mentioned laser beam having a wavelength of 650 nm. Further, the optical head 20b is a reproducing optical head, and irradiates the above-described laser beam having a wavelength of 780 nm,
A hologram laser unit 22 that generates a reproduction signal from the reflected light is built in. Each of the optical heads 20a and 20b of the optical recording device 10 has a different slide mechanism 4.
0a and 40b, so that focus servo and tracking servo can be individually performed. Therefore, in the optical recording device 10 of the present embodiment, a process of recording information using the laser driving power supplied from the recording circuit 13 using the optical head 20a, and supplying a reproduction signal to the reproduction circuit 14 using the optical head 20b. Then, the process of reproducing information can be performed independently in different areas of the recording layer of the optical disc 1. For this reason, the optical recording apparatus 10 of the present example has a configuration in which monitoring of recorded information and rewriting of information can be easily performed.

The optical recording apparatus 10 of this embodiment is also an optical recording apparatus using a CD-R having wavelength selectivity as a recording medium (optical disk), and has a low reflectance and a high energy absorption rate of 650 nm. Can be used to record information on an optical disc. Further, it is possible to reproduce information recorded on the optical disk by using a laser beam having a wavelength of 780 nm, which has a high reflectance and provides a large reproduction signal. Therefore, the recording process can be performed by using a low-power semiconductor laser similarly to the above-described optical recording device, and can be provided at low cost, and the power consumption during recording can be significantly reduced. It is possible to provide an optical recording device with a high writing speed with the same power as that of the optical recording device. Further, at the time of reproduction, a large reproduction signal can be obtained, so that an S / N ratio can be increased, and an optical recording apparatus capable of reliably reproducing information with a high recording density at high speed can be provided.

[Embodiment 3] FIG. 4 shows an example of a different optical recording apparatus according to the present invention. Optical recording device 10 of the present example
As in the first embodiment, a single optical head 20 can irradiate laser beams of different wavelengths from one optical head 20, and as an optical recording medium (optical disc), a writable optical recording medium (DVD) having a higher recording density than a CD-R and a DVD standard is used. -R) A device capable of recording and reproducing data for 2. A DVD (Digital Video Disk) is an optical disk having a higher recording density than a CD. The specification that the track pitch of a CD is 1.6 μm and the track pitch is 0.74 μm is standardized. On the other hand, recording and reproducing using a laser beam having a wavelength of 650 nm or 635 nm has been considered. Phase change type recordable DVD-R
Shows a low reflectance of 10% or less for a laser beam having a wavelength of 500 to 600 nm as shown in FIG.
It shows a very high reflectivity of around 90% for a laser beam having a wavelength of 650 nm.

Therefore, the optical recording apparatus 10 of this embodiment employs a semiconductor laser unit 41 for irradiating green laser light 43 of 500 to 600 nm for writing.
A semiconductor laser unit 42 for irradiating infrared laser light 44 of 635 to 650 nm for reproduction is employed. Then, the laser beams 43 and 44 emitted from the respective laser units 41 and 42 are collimated by the collimator lens 2.
The light beams are converted into parallel light beams by 5 and 26, and are incident on an objective lens 28 via the same optical path by a dichroic prism 27. The respective laser beams 43 and 44 are corrected for chromatic aberration and the like generated in the objective lens 28 by the respective collimator lenses 25 and 26, and the respective laser beams 43 and 44 emitted from the objective lens 28 Recording layer 2
The light is focused on a.

Each of the semiconductor laser units 41 and 42 provided in the optical head 20 of this embodiment has no light receiving function, and the reflected light from the optical disk 2 is incident on the optical head 20 by the objective lens 28. Later, the light is separated by the half prism 45 and the collimator lens 4
The light is condensed on a light-receiving sensor 48 via an optical element 47 that generates astigmatism. In the sensor 48, a signal for tracking and focusing control of the optical head 20 and a reproduction signal for reproducing information are generated from the reflected light, and supplied to the servo control circuit 11 and the reproduction circuit 14, respectively. Since the servo control mechanisms 11 and 12 and the recording circuit 13 for generating power for driving the laser are the same as those in the above-described embodiment,
A common number is assigned and the description is omitted.

In the optical recording apparatus 10 of this embodiment, a DVD
Information can be recorded on a DVD-R, which is a writable medium of the standard, by using a laser beam 43 having a low reflectance of 500 to 600 nm, while a high reflectance 6 is used.
A high-intensity reproduced signal can be obtained by the laser beam 44 of 35 to 650 nm. By performing recording and reproduction using laser light in such a wavelength band, as in the optical recording apparatus described above, a wavelength having a low reflectance and a high absorption for a DVD-R having a high recording density. The recording process can be performed using a low power semiconductor laser. Further, a high reproduction signal can be obtained by a laser beam having a wavelength with a high reflectivity, and information with a high recording density can be reliably reproduced at high speed.
For example, when a laser beam having a wavelength of 635 to 650 nm is used for recording and reproduction, it is necessary to use a semiconductor laser having an output of 50 mW to perform writing and to secure energy of about 10 mW on the surface of the optical disc 2. is there. On the other hand, in the optical recording device 10 of the present example,
The energy of about 10%, that is, about 1 mW of the energy of the surface of the optical disk 2 may be secured by the laser light of 500 to 600 nm, so that the recording processing can be performed by a low power semiconductor laser of about 5 mW. vice versa,
If a semiconductor laser of about 50 mW is provided, 10
It is possible to record at a very high speed of about double speed,
It is possible to provide an optical recording device 10 suitable for a large-capacity DVD with a high recording density.

In the optical recording apparatus described above, the optical head itself is tracked or focused by a magnetic actuator, but the objective lens 28 can be individually servo-controlled.
Further, the above-described optical system is merely an example of the present invention, and an optical system for correcting chromatic aberration or the like is added, or
An optical system such as providing an objective lens for each laser beam of each frequency can also be adopted. Optical heads and optical recording devices having these optical systems are also included in the scope of the present invention.

[0022]

As described above, in the present invention,
By using an optical recording device capable of irradiating two laser beams having different wavelengths and an optical head suitable for the laser, a laser having a wavelength suitable for the recording process and a reproducing process for an optical recording medium having wavelength selectivity is used for each process. It becomes possible to irradiate light. At the time of recording, by selecting a wavelength belonging to a wavelength band having a low reflectance of the optical recording medium, sufficient energy can be given to the optical recording medium to perform recording even with a low-power laser beam. , During playback,
By selecting a wavelength belonging to a wavelength band having a high reflectance of the optical recording medium, a high-intensity reproduced signal can be obtained. Therefore, it is possible to realize an optical recording apparatus capable of performing a recording process using a low-power and inexpensive semiconductor laser.
-R or a DVD-R can be provided at an inexpensive optical recording device. Further, since recording can be performed with a low-power laser beam, power consumption during processing can be reduced. On the other hand, if writing is performed using a semiconductor laser having approximately the same power as conventionally thought, several to ten times as much energy can be applied to the optical recording medium, and therefore several to ten times. A high recording speed can be realized, and an optical recording apparatus suitable for an optical recording medium having a high recording density and a large capacity can be realized in the future.

In reproduction, high-intensity reflected light is obtained by using a laser beam having a high reflectivity, and a reproduced signal having a high S / N ratio can be obtained. For this reason, the reproduction speed is high and the reproduction process with high reliability is possible, and a large amount of information can be reproduced reliably and quickly. As described above, the optical recording / reproducing method, the optical recording apparatus, and the optical head of the present invention can record with a low-power laser beam, which is impossible with a conventional recording / reproducing method using one kind of laser beam. Processing and reproduction processing that can obtain a high-intensity reproduction signal can be realized simultaneously, and recording and reproduction can be performed reliably and at high speed on an optical recording medium with a high recording density and a large capacity and a wide range of applications. An optical recording apparatus capable of performing the above can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of an optical recording device according to an embodiment of the present invention.

FIG. 2 is a graph showing the reflection characteristics of a CD-R with respect to the wavelength of a laser beam.

FIG. 3 is a diagram showing a schematic configuration of an optical recording apparatus according to another embodiment of the present invention.

FIG. 4 is a block diagram showing a schematic configuration of an optical recording apparatus according to still another embodiment of the present invention.

FIG. 5 is a graph showing the reflection characteristics of a DVD-R with respect to the wavelength of a laser beam.

[Explanation of symbols]

 1, 2, optical disk 10, optical recording device 11, servo control circuit 12, 31, servo actuator 13, recording circuit 14, reproduction circuit 20, optical head 21, 22, hologram laser unit 23, 24, 43, 44 Laser light having different wavelengths 25, 26, 46 Collimator lens 27 Dichroic prism 28 Objective lens 29 Housing

Claims (7)

[Claims] 1. An optical recording / reproducing method for recording and reproducing information by irradiating an optical recording medium with a laser beam, wherein: a recording step of recording the information using the laser beam of a first wavelength; A reproducing step of reproducing the information by using the laser light having a second wavelength different from the first wavelength. 2. The optical recording medium according to claim 1, wherein the first wavelength belongs to a wavelength band having a low reflectance of the optical recording medium, and the second wavelength belongs to a wavelength band having a high reflectance of the optical recording medium. An optical recording / reproducing method characterized by the above-mentioned. 3. A laser light source for emitting first and second laser beams having different wavelengths, and an optical system capable of condensing the first and second laser beams on the same recording layer of an optical recording medium. An optical head, characterized in that: 4. The method according to claim 3, wherein the wavelength of the first laser beam belongs to a wavelength band where the reflectance of the optical recording medium is low.
The optical head according to claim 1, wherein a wavelength of the second laser beam belongs to a wavelength band where the reflectance of the optical recording medium is high. 5. An optical head capable of converging first and second laser beams having different wavelengths on the same recording layer of an optical recording medium;
An optical recording apparatus, comprising: a recording unit that records information on the recording medium with the first laser beam; and a reproducing unit that reproduces information recorded on the recording medium with the second laser beam. . 6. A first optical head capable of condensing a first laser beam on a recording layer of an optical recording medium to record information, and a second laser beam having a different wavelength from the first laser beam. An optical recording device comprising: a second optical head capable of condensing light on a recording layer and reproducing the information. 7. The wavelength of the first laser light according to claim 5, wherein the wavelength of the first laser light belongs to a wavelength band where the reflectance of the optical recording medium is low, and the wavelength of the second laser light is the reflection of the optical recording medium. An optical recording device belonging to a wavelength band having a high rate.