JPH08315364A - Optical disk recording/reproducing device - Google Patents

Abstract

PURPOSE: To provide an optical disk recording/reproducing device capable of performing a high density recording by recording an information signal of a channel with an excellent characteristic at the best data rate. CONSTITUTION: The pickup of the optical disk recording/reproducing device is constituted of a laser diode 1 emitting four beams of laser light, a collimate lens 2, a grating 3 dividing the beam of the laser light, a beam splitter 4, a 1/4 wavelength plate 5 rotating the phase of the wavelength of the laser light by 1/4 wavelength, an objective lens 6, a cylindrical lens 8 and a photodiode 9 as a photodetector. The information signal among four channels is recorded by changing the data rate of respective channels according to the optical characteristic or the electrical characteristic of the pickup.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc recording / reproducing apparatus for recording multi-channel information signals with high density.

[0002]

2. Description of the Related Art Conventionally, in an optical disk recording / reproducing apparatus, information signals are recorded / reproduced by using an optical pickup. The optical pickup consists of a laser diode, which is a light source, a collimator lens that collimates the laser light into a parallel light flux, an objective lens that focuses the parallel light flux into a small spot on the pit surface of the optical disc, and a disc surface with pits that returns the light. It consists of a photodiode that detects incoming light, a quarter-wave plate that separates the emitted light and the reflected light, a beam splitter, a cylindrical lens, and the like.

When performing multi-channel recording using a multi-beam laser, the optical head can be miniaturized by using the same optical component for the laser beam of each channel. However, the optical path of the laser beam of each channel is different for each channel. For example, in the channel passing through the center of the lens and the channel passing through the end, the former has better optical characteristics. This is because the aberration of the lens and the intensity distribution of the laser are different. In addition, the former has better electric characteristics. This is because the central portion of the laser diode or the photodiode has good light emitting characteristics and light receiving characteristics.

In the case of multi-channel recording, the transfer rate of each channel is adapted to the transfer rate determined by the channel having the lowest optical characteristic or electric characteristic for the above reason. For this reason, the margin of the optical characteristic or the electric characteristic of the channel having other favorable characteristics cannot be used and is wasted.

Further, when performing multi-channel recording, there are cases where recording is performed separately for each channel on the inner and outer peripheries of the disc, and there is a case where recording and reproducing are performed by multi-beams passing through the same objective lens. In the latter case, the channels passing through the same objective lens have the same transfer rate as the data rate. At this time, since the optical path is different for each channel, the optical characteristics are different. The data rate was determined by the channel with the lowest characteristic, and the margin for the channel with good characteristics was wasted.

Alternatively, the frequency characteristics may differ for each channel depending on the characteristics of the light receiving element or the light emitting element.
In either case, the transfer rate is adjusted to the lowest characteristic, although there is still room for a channel with good characteristics. As a result, the data transfer rate is determined, which limits the improvement in recording density.

[0007]

As described above, in the conventional optical disk recording / reproducing apparatus, although there is still a margin in a channel having good characteristics among the multiple channels,
The transfer rate is adapted to the lowest characteristic. As a result, the data transfer rate is determined, which limits the improvement of the recording density, and there is a disadvantage that high recording density recording cannot be performed. It is an object of the present invention to provide an optical disc recording / reproducing apparatus capable of high density recording by solving such a problem and recording an information signal of a channel having good characteristics at the highest data rate.

[0008]

An optical disk recording / reproducing apparatus of the present invention irradiates a laser beam emitted from a light emitting element onto an optical disk through an optical lens, and reflects light from the light receiving element through the optical lens. In an optical disc recording / reproducing apparatus that receives light and records or reproduces information signals on the optical disc, when recording information signals on the optical disc on multiple channels by a plurality of laser beams emitted from a light emitting element, The data rate of the information signal to be recorded on is changed.

[0009]

The operation of the optical system of the optical pickup of the optical disk recording / reproducing apparatus thus constructed will be described. At the time of recording, a plurality of laser beams are emitted from the light emitting element, converted into parallel laser beams by the optical lens, and the laser beams are split into beams by the optical lens. Then, the laser light is passed through the optical system and the phase of the quarter wavelength of the laser light is rotated. Further, it passes through the optical system and is irradiated onto the optical disc. As a result, multi-channel information signals are recorded on the optical disc. The laser light reflected by the optical disk passes through the optical system, and the laser light is rotated by a quarter wavelength phase by the optical system. Since the half-wave phase of the laser light is rotated in the going and returning directions, the direction is changed by the optical system and is received by the light receiving element.

At the time of reproduction, a plurality of laser beams are emitted from the light emitting element and converted into parallel laser beams by the optical system, and the respective laser beams are divided into beams. Then, the laser light is passed through the optical system and the phase of the quarter wavelength of the laser light is rotated. Further, it passes through the optical system and is irradiated onto the optical disc. in this way,
The beam emitted from the light emitting element passes through the same optical lens and is irradiated onto the optical disc to be recorded.

The positions of the laser beams of a plurality of channels on the lens of each optical lens are as follows. On the lens, each beam passes with a certain distance.
The beam shown here is a main beam for recording or reproducing a signal. There are a laser beam of a channel passing near the center of the lens and a laser beam of a channel passing a position deviated from the center of the lens.

Since the lens has aberrations, the central portion has better frequency characteristics and graphic characteristics, and the more it is away from the center of the lens, the more it deteriorates. Therefore, the laser beam of the channel passing near the center of the lens has better recording / reproducing characteristics than the laser beam of the channel passing the position deviated from the center of the lens.

At this time, conventionally, when the transfer rate of the data to be recorded is set to be the same for each channel, it has been necessary to match the channel having the worst characteristic. However, in the present invention, the data transfer rate is determined according to the optical characteristic or electric characteristic of each channel. This makes it possible to realize a higher transfer rate.

In this case, the laser beam of the channel passing near the center of the lens may be set to a higher transfer rate than the laser beam of the channel passing the position deviated from the center of the lens. By setting the information signal of a channel having good optical characteristics or electric characteristics to a high transfer rate, high density recording becomes possible.

[0015]

First, the structure of an optical disk recording / reproducing apparatus to which this example is applied will be described. FIG. 5 is a block diagram showing the basic configuration of the optical disc recording / reproducing apparatus to which this embodiment is applied.
The optical disc recording / reproducing apparatus includes an optical disc 100 and an optical disc drive 101. The optical disc drive 101 irradiates a laser beam spot while rotating the optical disc to record and reproduce information. The optical disc drive 101 includes a spindle motor 102,
A rotation control system 103, an optical pickup 104, a coarse movement motor 105, a coarse movement motor control system 106, a signal processing system 107,
Pickup control system 108, drive controller 10
It is composed of 9.

The optical pickup 104 records an information signal on the optical disc and reproduces the information recorded on the optical disc. The optical pickup 104 has a function of detecting a shake of the surface due to the rotation of the disk and a shake of the track in the radial direction of the disk, and automatically adjusting the shake so that it is always within a certain error. Coarse motor 1
Reference numeral 05 causes the optical pickup 104 to move largely near the target position on the optical disc at high speed. The coarse motor 105 is
It is also used in cooperation with the motor in the optical pickup 104 to cause the laser light to follow the shake of the track on the disk.

The drive controller 109 controls the operation of each section of the optical disk reproducing apparatus. The drive controller 109 controls each control system according to an instruction from an external drive interface to perform a target operation. That is, according to the control signal of the drive controller 109, the rotation control system 103 rotates the spindle motor 102 and the optical disc 100. Further, in response to a control signal from the drive controller 109, the coarse movement motor control system 106 moves the coarse movement motor 105 to move the optical pickup 104 in the radial direction of the optical disc 100.

The drive controller supplies the information supplied from the external interface to the signal processing system 107. The signal processing system 107 performs signal processing such as modulation and error correction coding on the supplied information and supplies the information to the optical pickup 104. The optical pickup 104 records a signal on the optical disc. In addition, the signal processing system 107
Performs signal processing on the information reproduced by the optical pickup 104 and supplies it to the drive controller. The drive controller outputs information to the external interface. The signal processing system 107 is composed of a demodulation circuit for reproduced signals and an error correction circuit.

The pickup control system 108 comprises a tracking drive circuit and a focusing drive circuit. The pickup control system 108 controls tracking servo and focusing servo of the optical pickup 104 in accordance with a control signal from the drive controller 109 and a control signal from the signal processing system 107.

The optical disk reproducing apparatus having the above structure operates as follows. Drive controller 1
In response to the control signal from 09, the rotation control system 103 rotates the spindle motor 102 and the optical disc 100. Further, in response to a control signal from the drive controller 109, the coarse motion motor control system 106 causes the coarse motion motor 10 to
5 to move the optical pickup 104 to the optical disc 100.
Move in the radial direction.

The pickup control system 108 controls the tracking servo and the focusing servo of the optical pickup 104 by the control signal of the drive controller 109 and the control signal of the signal processing system 107. The optical pickup 104 records an information signal on the optical disc and reproduces the information recorded on the optical disc. The optical pickup 104 detects the shake of the surface due to the rotation of the disk and the shake of the track in the disk radial direction, and records or reproduces information while automatically adjusting the shake so that it is always within a certain error. .

At the time of recording, the drive controller receives information supplied from an external interface from the signal processing system 1.
Supply to 07. The signal processing system 107 subjects the supplied information to signal processing such as modulation and error correction coding and supplies the information to the optical pickup 104. Optical pickup 104
Records a signal on the optical disc. Also, during playback,
The signal processing system 107 performs signal processing such as demodulation and error correction on the information reproduced by the optical pickup 104 and supplies the information to the drive controller. The drive controller outputs information to the external interface. like this,
The optical pickup 104 in the optical disk reproducing apparatus records or reproduces information signals on the optical disk in multiple channels.

Bell for recording / reproducing in 4 channels using a multi-beam laser. FIG. 1 shows the structure and optical path of an optical pickup for recording / reproducing on four channels by using the multi-beam laser of this embodiment. This pickup includes a laser diode 1 that emits four laser beams, a collimator lens 2, a grating 3 that divides the laser beam, a beam splitter 4, and a quarter-wave plate that rotates the phase of the wavelength of the laser beam by a quarter wavelength. 5, an objective lens 6, a cylindrical lens 8, and a photodiode 9 as a light receiving element.

The laser diode 1 emits four laser beams. The laser diode has four independent semiconductor light emitting devices in one package. The signal processing system 107 shown in FIG.
By modulating with the modulation circuit inside, 4-channel recording becomes possible.

Here, the semiconductor laser diode has the following characteristics. The oscillation wavelength is generally 780 [nm], but from the viewpoint of improving the recording density, a short wavelength laser that can narrow the beam diameter is preferable. Beam emission angle: expressed in full width at half maximum, 25 in horizontal transverse mode
Degrees of 45 to 45 degrees, and vertical and horizontal modes of 8 to 15 degrees are used. Polarization characteristics: Linearly polarized light with an electric field component parallel to the joint surface is emitted. However, in reality, there is a polarized component also in the direction perpendicular to the joint surface. The ratio of the polarization component parallel to the joint surface and the polarization component perpendicular to the joint surface is called the polarization ratio, and there are about 100.

Astigmatic difference: The beam waist in the direction perpendicular to the joint surface is designed to coincide with the resonator end face, but in the parallel direction it is located slightly inside the end face. If this distance is an astigmatic difference and becomes large, a correction optical system for condensing the spot on the disk is required. The astigmatic difference of the gain-guided laser is 10 to 50 [μm]. In the index-guided laser, the beam waist in the direction parallel to the junction surface is also made to substantially coincide with the cavity end face, and the astigmatic difference is 5 [μ
m] or less. If the astigmatic difference is small, there is no need for a correction optical system to focus the light, and the optical pickup can be made compact.
Can be lightened.

Oscillation mode: The oscillation frequency characteristic (oscillation spectrum) of a semiconductor laser has a spectrum with a narrow frequency width, and a characteristic having one spectrum is called a longitudinal single mode and a characteristic having two or more spectra. Is called vertical multi-mode. For applications where noise is a concern, longitudinal multimode lasers are preferred. When the output of the semiconductor laser is changed, the spectrum of the longitudinal mode changes. When the optical output is low power, many longitudinal modes oscillate simultaneously, and when the power exceeds a certain value, the output is concentrated in one mode. .
When the light output is further increased or the external temperature is raised, the junction temperature rises, and the modes jump to the longer wavelength side one after another. When the longitudinal mode jumps due to changes in temperature or current, the light output changes. If this jump continues, the output fluctuation becomes noise.

Input-output characteristics: Shows the relationship between the applied current and the output of laser light. The current value at which the optical output sharply rises is called the threshold current, and laser oscillation is started from the point at which this value is exceeded. The threshold current increases with temperature. The average increase value of the optical output per unit drive current in the laser oscillation region is called the differential efficiency, which indicates the good oscillation efficiency. Noise characteristics: There are noise generated when jumping in the longitudinal mode and return light noise caused by the change of the oscillation mode due to the return light. When the light return rate is small, the noise is extremely low. Noise is reduced even when high-frequency modulation is performed to provide multiple modes. Reliability: Life of semiconductor laser depends on ambient temperature, operating current,
It depends on the light output, etc. There is a close relationship between the junction temperature during use and the service life, and as the temperature increases, the service life exponentially shortens. Therefore, use as low a current as possible and consider heat dissipation. These characteristics may vary from channel to channel depending on the laser diode itself and on the position of the laser beam on the lens. This difference in characteristics is checked in advance for each channel to grasp which channel has good or bad characteristics.

The collimator lens 2 converts the incident diverging laser beam into a parallel laser beam. The grating 3 divides the beam of laser light. The beam splitter 4 is a half mirror lens that transmits the incident laser beam and reflects the reflected laser beam at an angle of 45 degrees. The quarter-wave plate 5 sets the phase of the wavelength of the laser light to 1
Turn / 4 wavelength. Since the quarter wavelength plate 5 rotates the phase of the wavelength of the incident laser light by a quarter wavelength and further rotates the phase of the wavelength of the reflected laser light by a quarter wavelength, the wavelength of the half wavelength laser light is rotated in total. .

The objective lens 6 is a lens forming a spot on the optical disk 7. The objective lens 6 has a function of focusing laser light on the disk with almost no aberration and collecting light scattered and diffracted by the tracks on the disk surface. Here, the objective lens has the following characteristics. Used wavelength: 780 [nm] or so. Numerical aperture (NA): NA = n'sin θ ₂ = nsin θ ₁
(N 'is the refractive index of air, and n is the refractive index of the disk). When the oscillation wavelength of the semiconductor laser is near 780 [nm], NA = 0.47 to obtain a signal with a good SN ratio.
0.52 is used.

Working distance: The working distance is the distance between the end surface of the lens barrel and the disk surface. A longer working distance can prevent the lens from colliding with the disc due to surface wobbling of the disc, but the focal length becomes large, resulting in a large objective lens. Focal length: The larger the focal length is, the larger the objective lens is. Therefore, in order to secure a working distance, the focal length of the objective lens is about 4.5 [mm]. Transmittance: Objective lens for optical pickup is 780 [n
m] or around 830 [nm] has good glass transmittance and short overall lens length, so absorption in glass
Internal loss due to scattering is negligible. Therefore, the transmittance is
It is determined by the reflection loss at the lens surface. The objective lens is composed of a plurality of single lenses. The three-lens configuration has a transmittance of 97% to 98%. An antireflection coat is applied to the surface of each lens. Without the antireflection coating, the reflected light of the objective lens is superimposed on the signal light reflected from the disk and reaches the photodiode, so that the detection sensitivity of the photodiode is lowered.

Maximum image height and maximum angle of view: The maximum image height is the maximum height of the image formed on the disc. Since the objective lens is moved parallel to the disk surface for tracking, the maximum image height is theoretically zero, but it is 0.2 to 0.3 [mm] due to an alignment error. The maximum angle of view is the angle of incident light that enters the objective lens. Since the parallel light image is incident, the maximum angle of view is theoretically zero.

The lens performance is said to be diffraction limited when the geometric aberrations are small enough that the spot size is diffraction limited. As the performance of the objective lens of the optical pickup, the diffraction limit performance is required because it is necessary to reduce the spot diameter and detect the mark on the disk by using the diffraction phenomenon. Here, the following are optical evaluation scales for lenses that require diffraction-limited performance.

Wavefront aberration: Light from one object point enters the lens as a spherical wave. If this lens has no aberration, it is emitted from the lens as a spherical wave that converges to the ideal image point. On the contrary, if the lens has aberration, the wavefront of the emitted light is deformed and is not a spherical wave. The deviation of this wavefront from the spherical wave is called wavefront aberration. The magnitude of the wavefront aberration can be expressed by how much the wavefront deviates from the spherical surface centered on the ideal image point. When the wavelength used is λ, the wavefront aberration is set to satisfy 0.07λ.

OTF (Optical Transfer)
(Fer Function): An optical system is a transmission system for information, like a circuit for electric signals, because it conveys the shape, arrangement, color, etc. of an object by light. The performance of this transmission system is evaluated by how accurately the original object or signal is transmitted. The OTF is a frequency filter of an optical system. These characteristics may vary from channel to channel depending on the objective lens itself and on the position of the laser beam on the lens. This difference in characteristics is checked in advance for each channel to grasp which channel has good or bad characteristics.

The cylindrical lens 8 is a cylindrical lens having a lens action only in one direction of the laser beam. The photodiode 9 is a light receiving element that receives the laser beam focused by the cylindrical lens 8 and detects an electrical signal by the light receiving spot. Here, the photodiode has the following characteristics.

Current-voltage characteristics: When a reverse voltage is applied, almost no current flows. A current flows when a forward voltage is applied. When the photodiode is irradiated with light, a photo-short circuit current proportional to the intensity of the light flows. This current value is proportional to the area of the element. Spectral sensitivity: Photocurrent is generated when the wavelength becomes shorter than the wavelength of light having energy larger than the forbidden bandwidth. The shorter the wavelength, the lower the spectral sensitivity.

Reverse bias characteristic: The range of rise time and linearity can be expanded by applying a reverse bias voltage. Applying an excessive voltage may increase noise and cause damage. Response speed: Expressed as the time from the time of light irradiation until the current generated thereby flows. The response speed is represented by the rise time or fall time of the current with respect to the stepwise optical input, and is represented by the time when the output changes from 10% to 90% of the steady value. The rise time is determined by the time constant determined by the terminal junction capacitance and load resistance, and the diffusion time of electrons and holes generated outside the depletion layer. In order to obtain a fast response speed, the junction capacitance may be reduced and a reverse bias voltage may be applied before use.

Signal separation characteristics: Focusing servo system,
For receiving the laser light in the tracking servo system, the light receiving portion is divided into a plurality of parts such as two or four parts to meet the specifications of the optical system. In the case where the light receiving parts are closely integrated, the signal separation characteristic between the light receiving parts is poor. When a reverse bias voltage is applied, the degree of signal separation increases. Noise: Thermal noise and shot noise are sources of intrinsic noise generated by the photodiode itself. Thermal noise is present in anything that has a resistance. Shot noise is observed as fluctuations in current.

Temperature characteristics: The sensitivity of the photodiode and the dark current change with changes in ambient temperature. The change in sensitivity is caused by the light absorption coefficient. The change in dark current depends on the probability that electrons in the lower energy band are excited to the upper band by heat, and therefore changes at a constant rate with respect to temperature change. This rate approximately doubles with a temperature rise of 5 ° C to 10 ° C. These characteristics can vary from channel to channel depending on the photodiode itself and on the position of the laser beam on the lens. This difference in characteristics is checked in advance for each channel to grasp which channel has good or bad characteristics. Then, in accordance with these optical characteristics or electrical characteristics, the information signal of the channel having good characteristics is recorded at a high data rate. This enables high density recording.

The operation of the optical system of the optical pickup thus constructed will be described. At the time of recording, four laser beams are emitted from the laser diode 1, converted into parallel laser beams by the collimator lens 2, and each laser beam is split by the grating 3. Then, the light is transmitted through the beam splitter 4, and the laser light is quartered by the quarter wavelength plate 5.
The wavelength phase is rotated. The disc 7 is irradiated through the objective lens 6. As a result, multi-channel information signals are recorded on the disc 7. The laser light reflected by the disk 7 passes through the objective lens 6 and the quarter-wave plate 5 rotates the quarter-wave phase of the laser light. Since the phase of the laser light is ½ wavelength in going and returning, the direction is changed by the beam splitter 4, enters the cylindrical lens 8, and is received by the photodiode 9.

At the time of reproduction, four laser beams are emitted from the laser diode 1 and converted into parallel laser beams by the collimator lens 2, and each laser beam is emitted by the grating 3.
The beam splits at. Then, the laser light is transmitted through the beam splitter 4, and the quarter-wave plate 5 rotates the quarter-wave phase of the laser light. The disc 7 is irradiated through the objective lens 6. In this way, the beam emitted from the light emitting element passes through the same optical component and is applied to the disk to be recorded. At this time, the respective beams pass through the same objective lens 6.

FIG. 2 shows the positions of four-channel laser beams on the lens of this embodiment. On the lens, each beam passes with a certain distance as shown in FIG. The beam shown here is a main beam for recording or reproducing a signal. There are channels such as the beam 22 and the beam 23 that pass near the center of the lens 20, and channels such as the beams 21 and 24 that pass through the positions deviated from the center of the lens 20.

Since the lens 20 has aberrations, the central portion has better frequency characteristics and graphic characteristics, and the farther from the center of the lens 20, the more deteriorated. Therefore, the beam 21 and the beam 24
Has poorer recording / reproducing characteristics than the beams 22 and 23. At this time, when the transfer rate of the data to be recorded is the same for all four channels, it is necessary to match the channel with the worst characteristic. However, in this example, the data transfer rate is determined according to the optical or electrical characteristics of each channel. This allows
A higher transfer rate can be realized. In the case of FIG.
Beam 22 and beam 23 having good optical and electrical characteristics
May be set to a higher transfer rate than the beams 21 and 24. High-density recording is possible by setting a high transfer rate.

A modified example of this example is shown below. When the photodiode configuration differs depending on the channel. When the optical disk is reproduced, the beam returning from the disk is as shown in FIG. 3 on the photodiode. FIG. 3 shows the structure of a 4-channel photodiode and the laser beam position.

The structure of the photodiode shown in FIG. 3 is as follows. The light receiving elements A, B, C and D are photodiodes that receive a laser beam of one channel. The light receiving element E is a photodiode that receives a two-channel laser beam. The light receiving element F is a photodiode that receives a three-channel laser beam. The light receiving elements G, H, I, and J are photodiodes that receive a 4-channel laser beam. The photodiodes for receiving the 1-channel and 4-channel laser beams respectively include four light receiving elements A, B, C, D and light receiving elements G, H, I, J. The photodiodes that receive the laser beams of 2 channels and 3 channels are respectively composed of one light receiving element E and one light receiving element F.

The number of photodiodes differs depending on the laser beams of different channels because it is necessary to divide and receive light for tracking. Here, since the capacitance of the light receiving element is different when the signal is received by the four elements and when the signal is received by the one element, the frequency characteristics are different. This is because the capacitance of the light receiving element increases as the number of elements increases. FIG. 4 shows frequency characteristics when the capacitance of the light receiving element of the photodiode is different.

FIG. 4 shows the frequency characteristic of the preamplifier measured at 3 pF per element, and FIG. 4A shows the characteristic of the input capacitance of 3 pF when the signal is received by one element. The characteristic of the input capacitance of 12 pF is shown in the frequency characteristic when the signal is received by the four elements. In this case, the beam 2 received by the light-receiving element E and the beam 3 received by the light-receiving element F have good characteristics because the frequency characteristics are extended to a high band. That is, a high level can be maintained over a wide frequency band. On the other hand, the beam 1 received by the light receiving element A, the light receiving element B, the light receiving element C, and the light receiving element D and the beam 4 received by the light receiving element G, the light receiving element H, the light receiving element I, and the light receiving element J have frequency characteristics as compared with the former. The level does not extend to the high band. That is, the level decreases in the high frequency band. Therefore, the former transfer rate can be set higher than the latter transfer rate. As a result, the transfer rate is increased by the amount set higher and high density recording becomes possible.

As another example, the case of using a plurality of lasers will be described below. When using multiple laser diodes instead of multi-beam laser diodes, use laser diodes with different wavelengths. In this case, if the wavelength is different, the OTF is different, and the shorter the wavelength, the better the frequency characteristic. Further, when the intensity distribution of the light beam differs depending on the laser, the OTF of the optical system differs, and the shorter the wavelength, the better the frequency characteristics. Therefore, if the recording data rate is determined for each wavelength, high density recording becomes possible. Further, since the intensity distribution of the light beam varies depending on the laser, it is possible to set a recording data rate suitable for each and perform high density recording.

Another example will be described below. In the optical disk recording / reproducing apparatus, there are a case of recording with multiple channels, a case of recording separately on the inner and outer circumferences of the disk, a case of dividing each disk, and a case of dividing a beam passing through one objective lens. In any of these cases, this example can be similarly applied.

[0051]

According to the present invention, the laser beam emitted from the light emitting element is irradiated onto the optical disk through the optical lens, and the reflected light is received by the light receiving element through the optical lens and the information is recorded on the optical disk. In an optical disk recording / reproducing apparatus for recording or reproducing a signal, when an information signal is recorded on an optical disk in multiple channels by a plurality of laser beams emitted from a light emitting element, the data rate of the information signal recorded for each channel Since it has been changed, it is possible to record at a high data rate on a channel with a margin without adjusting the data rate of each channel to the data rate of the channel with the minimum condition, so high density recording is possible. Become.

Further, according to the present invention, in the above,
Of the multi-channel information signals, the information signal of the channel with good optical characteristics is recorded at the high transfer data rate, and the information signal of the bad channel is recorded at the low transfer data rate, so the optical characteristics are maximized. High density recording can be performed by utilizing this.

Further, according to the present invention, in the above,
Since the data rate is changed and recorded according to the characteristic of the light receiving element, the information signal of the channel having the excellent characteristic of the light receiving element can be recorded at a higher data rate.

Further, according to the present invention, in the above,
Since the data rate is changed and recorded according to the characteristics of the light emitting element, the information signal of the channel having the good characteristics of the light emitting element can be recorded at a higher data rate.

Further, according to the present invention, in the above,
Of the multi-channel information signals, the information signal of the channel with good electric characteristics is recorded at the high transfer data rate, and the information signal of the bad channel is recorded at the low transfer data rate, so that the electric characteristics can be used to the maximum. Therefore, high density recording can be performed.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration and an optical path of an optical pickup for recording / reproducing on four channels using a multi-beam laser of an embodiment of an optical disc recording / reproducing recording apparatus of the present invention.

FIG. 2 is a diagram showing positions of 4-channel laser beams on a lens of an embodiment of the optical disk recording / reproducing apparatus of the present invention.

FIG. 3 is a diagram showing a structure of a 4-channel photodiode and a position of a laser beam of an embodiment of the optical disk recording / reproducing apparatus of the present invention.

FIG. 4 is a diagram showing frequency characteristics when the capacitance of the light receiving element of the photodiode of the embodiment of the optical disc recording / reproducing recording apparatus of the present invention is different.

FIG. 5 is a block diagram showing a basic configuration of an embodiment of an optical disc recording / reproducing recording apparatus of the present invention.

[Explanation of symbols]

 1 Laser Diode 2 Collimator Lens 3 Grating 4 Beam Splitter 5 1/4 Wave Plate 6 Objective Lens 7 Optical Disk 8 Cylindrical Lens 9 Photodiode 20 Lens 21 Beam 22 Beam 23 Beam 24 Beam 30 Photodiode 31 Beam 32 Beam 33 Beam 34 Beam A , B, C, D, E, F, G, H, I, J Light receiving element 104 Optical pickup

Claims (5)

[Claims] 1. A laser beam emitted from a light emitting element is irradiated onto an optical disk through an optical lens, and reflected light is received by a light receiving element through the optical lens to record or reproduce an information signal on the optical disk. In the optical disc recording / reproducing apparatus for performing, when the information signal is recorded on the optical disc in multiple channels by the plurality of laser beams emitted from the light emitting element, the data rate of the information signal to be recorded is changed for each channel. An optical disk recording / playback recording apparatus characterized by the above. 2. The optical disc recording / reproducing apparatus according to claim 1, wherein, of the multi-channel information signals, the information signal of a channel having good optical characteristics is recorded at a high transfer data rate,
An optical disc recording / reproducing apparatus characterized in that a bad channel information signal is recorded at a low transfer data rate. 3. The optical disk recording / reproducing apparatus according to claim 1, wherein the recording is performed while changing the data rate depending on the characteristics of the light receiving element. 4. The optical disc recording / reproducing apparatus according to claim 1, wherein the recording is performed while changing the data rate depending on the characteristics of the light emitting element. 5. The optical disc recording / reproducing apparatus according to claim 1, wherein, of the multi-channel information signals, the information signal of a channel having good electric characteristics is recorded at a high transfer data rate,
An optical disc recording / reproducing apparatus characterized in that a bad channel information signal is recorded at a low transfer data rate.