JPH09231570A - Information recording/reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an information recording/reproducing device capable of obtaining a good S/N even in the region of an outer peripheral side in a ZCAV system. SOLUTION: Recording/reproducing is performed by dividing the full recording/reproducing surface of an optical disk 1 into several regions in a radial direction, for instance into the regions Z1 to Z5, and changing a recording/reproducing frequency for each region. Also, recording/reproducing is performed so that the minimum recording mark lengths of the respective regions Z1 to Z5, that is, the minimum recording mark lengths m1 to m5 of recording marks M1 to M5 in the innermost sides of the respective regions, are gradually increased from the region Z1 of the inner side to the region Z5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording / reproducing apparatus, and more particularly to an information recording / reproducing apparatus for rewritable optical disks such as MO (magneto-optical disk) and phase change type optical disks.

[0002]

2. Description of the Related Art Conventionally, when reproducing information from a rewritable optical disk such as an MO or a phase-change optical disk, optical output (laser output) during recording and erasing is performed so as not to erase or destroy recorded information. The information is reproduced with a constant light output which is sufficiently lower than the above.

On the other hand, in recent years, various methods have been used to increase the recording capacity of an optical disk. Basically, the interval between tracks to be recorded is narrowed to increase the recording density, and the minimum mark to be recorded is used. It is necessary to reduce the length of. In this case, particularly when the length of the mark to be recorded is gradually reduced, the signal amplitude of the reproduction signal corresponding to the mark becomes small due to the influence of the OTF (optical transfer function) of the optical system.

The reproduced signal contains amplifier noise in the reproducing amplifier, intensity fluctuation noise of the semiconductor laser of the optical disk medium or the light source, shot noise generated during photoelectric conversion in the detector, and the like. Therefore, when the signal amplitude corresponding to the mark becomes smaller as the mark length is shortened, the desired signal is buried in these noises, and the signal cannot be correctly reproduced. is there.

Conventionally, in high density recording, the entire surface of an optical disc is divided into several areas in the radial direction, and recording and reproducing are performed so that the minimum recording mark length in each area is approximately the same length. -CAV) method is applied. FIG. 7 is an explanatory diagram showing a recording format according to the conventional ZCAV system. In this case, the optical disc 1
Areas Z1 to Z5 are provided on the recording / reproducing surface of No. 1 in the radial direction.

The minimum recording mark lengths m1 to m5 of the innermost recording marks M1 to M5 in each of the areas Z1 to Z5 are substantially the same (m1). The length of the minimum recording mark in each area is determined by the optical disc 1
Since the rotation speed of 1 is constant (constant angular velocity), the minimum recording mark on the outer peripheral side has a longer mark length than the minimum recording mark on the inner peripheral side of the same area. In practice, by keeping the number of rotations constant and increasing the recording / reproducing frequency toward the outer peripheral area of the optical disc, the recording and reproducing are performed so that the minimum recording mark length becomes approximately the same in each area. It was

[0007]

Therefore, in such a conventional information recording / reproducing apparatus, since the recording / reproducing frequency is increased toward the outer peripheral side of the optical disk, a wide frequency band is required to reproduce the signal. On the other hand, the noise of the amplifier that amplifies the reproduced signal is thermal noise in a circuit and has the property of becoming larger as the frequency rises.Therefore, when reproducing the outer peripheral side where the recording / reproducing frequency of the disc is high, the inner peripheral side There is a problem that the noise becomes larger and the S / N ratio becomes worse.

The present invention is intended to solve such a problem, and it is an object of the present invention to provide an information recording / reproducing apparatus capable of obtaining a good S / N ratio even in the area on the outer peripheral side in the ZCAV system. Has an aim.

[0009]

In order to achieve such an object, the information recording / reproducing apparatus according to the present invention has an outer peripheral side as compared with a minimum recording mark length in an inner peripheral side area of each area. The minimum recording mark length in the area is slightly increased. Therefore, recording / reproduction is performed such that the minimum recording mark length in the outer peripheral area is larger than the minimum recording mark length in the inner peripheral area.

Further, a low-pass filter which is provided after the amplifier for amplifying the reproduced signal and removes noise in the high frequency band generated in the amplifier on the basis of an arbitrary cutoff frequency, and the low-pass filter is reproduced. And a control means for setting a cutoff frequency corresponding to the position information of the track being reproduced detected from the signal.
Therefore, the cut-off frequency corresponding to the position information of the track being reproduced detected from the reproduction signal is set for the low-pass filter.

[0011]

Next, the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing a recording format of an optical disc by an information recording / reproducing apparatus according to an embodiment of the present invention, and the same or similar parts as those described above (see FIG. 7) are denoted by the same reference numerals. Conventional ZCAV (ZON
In the E-CAV system, the entire recording / reproducing surface of the optical disk 11 is divided into several areas in the radial direction, and recording and reproduction are performed so that the minimum recording mark lengths of the respective areas are almost the same. However, in the present invention, recording / reproduction is performed so that the minimum recording mark length for each area gradually increases from the area on the inner peripheral side.

Generally, when the optical disk 11 is rotated at a constant rotation speed (constant angular velocity) based on the ZCAV system, the linear velocity increases toward the outer peripheral area, and the relationship between the optical disc radius and the recording / reproducing frequency. As shown in FIG. 2, the recording / reproducing frequency rises stepwise according to the recording area as the radius of the optical disc increases. Here, if a cut-off frequency is set to a frequency that is 2 to 3 times the recording / reproducing frequency by providing a low-pass filter after the IV conversion amplifier that amplifies the reproducing signal, as shown in FIG. The higher the level, the higher the level of amplifier noise in the IV conversion amplifier.

As a result, when compared with the same signal amplitude, the higher the recording / reproducing frequency in the outer peripheral area, the lower the S / N ratio, the larger the detection error rate of the reproduced signal, and the more reliable the reproduced signal. It will decrease. On the other hand, the relationship between the minimum recording mark length and the carrier level (the signal amplitude of the reproduction signal) is as shown in FIG. 4, and the boundary of the OTF limit region, in this example, the minimum recording mark length of around 0.6 μm. You can see that the carrier level is increasing rapidly.

Therefore, since the amplifier noise level is low in the area Z1 on the inner circumference side of the optical disk 11, that is, the area where the recording / reproducing frequency is low, the lower limit side of the OTF limit area, for example, the minimum recording mark length m1 is 0.56 to 0.58 μm. Further, since the amplifier noise level is high in the outer peripheral side area Z1 of the optical disk 11, that is, the area where the recording / reproducing frequency is high, the upper limit side of the OTF limit area, for example, the minimum recording mark length m5 is 0.62. It should be set to be 0.64 μm. Further, the minimum recording mark length in the area between them is gradually increased from m1 to m5 (m1 <m5).

As a result, for example, in comparison with the conventional case where the minimum recording mark length is fixedly set to 0.60 μm in each of the areas Z1 to Z5 on the optical disk 11, variations in amplifier noise due to changes in the recording / reproducing frequency are suppressed. A high S / N ratio can be stably obtained in each of the areas Z1 to Z5 of the optical disk 11 without being affected, and high reliability can be obtained in the recording / reproducing operation. Further, the change in recording capacity due to this is extremely small, and a recording capacity almost equal to that of the conventional ZCAV system can be obtained.

FIG. 5 is a block diagram showing a reproduction signal system of the information recording / reproducing apparatus according to the embodiment of the present invention. Here, the entire surface of the recording / reproducing surface of the optical disc is divided into several areas in the radial direction, and ZCAV (recording / reproducing is performed so that the minimum recording mark length in each area gradually increases from the area on the inner circumference side). The case where the ZONE-CAV method is applied will be described as an example.

In FIG. 5, reference numeral 1 denotes a semiconductor laser (not shown) for irradiating the optical disc 11 with a light beam (laser light), an objective lens (not shown), and a PIN photo for detecting reflected light from the optical disc 11. An optical head 2 having a diode (not shown) for recording / reproducing information on / from an arbitrary track provided on the recording / reproducing surface of the optical disc 11 is based on the detection output from the PIN photodiode of the optical head 1. And a reproduction signal detector for detecting a reproduction signal indicating various kinds of recorded information.

Reference numeral 3 denotes an IV conversion amplifier for converting the reproduction signal output from the reproduction signal detector 2 into current / voltage and amplifying it. Reference numeral 4 denotes a waveform equalization circuit for equalizing the waveform of the reproduction signal from the IV conversion amplifier 3. Is a low-pass filter that removes high-band frequency noise components from the output of the waveform equalization circuit 4, and 6 is a signal in which the noise components have been removed by the low-pass filter 5 is converted into binarized data and recorded on the optical disc 11. MO signal 12 indicating user data and I indicating address data
It is a binarization circuit that outputs the D signal 13.

Further, 7 is an ID signal 1 from the binarization circuit 6.
An ID detection / read circuit for detecting various position information on the recording / reproducing surface of the optical disk 11 based on 3, an I / O circuit for inputting / outputting various signals, and a 9 input through the I / O circuit 8. Optical disc 11 based on various position information
The radial position of the optical head 1 on the recording / reproducing surface is calculated, and control information such as the minimum recording mark length and the recording / reproducing frequency according to the radial position is stored in the memory (ROM / RAM) 10.
It is a CPU (control means) that controls each unit by reading out from the unit and outputting a predetermined control signal based on the control information to each unit via the I / O circuit 8.

Next, the operation of the present invention will be described with reference to FIG. The light beam (laser light) emitted from the semiconductor laser of the optical head 1 to the recording / reproducing surface of the optical disk 11 rotating at a constant number of revolutions (constant angular velocity) is reflected on the recording / reproducing surface and the PIN of the optical head 1 is reflected. It is detected and output by the photodiode. On the recording / reproducing surface of the optical disk 11, recording units called sectors 21 as shown in FIG. 6 are provided along the tracks provided in the circumferential direction.

The position information (ID signal: track number, address number) of the sector is recorded in the address portion 22 located at the head of the sector 21, and arbitrary information (MO signal)
Is recorded. The reproduction signal detector 2 detects a reproduction signal indicating various information recorded in such a sector based on the detection output from the PIN photodiode. This reproduction signal is current / voltage converted and amplified by the IV conversion amplifier 3, and waveform equalization is performed by the waveform equalization circuit 4 so that the frequency characteristics corresponding to each mark length are made uniform.

Subsequently, the low-pass filter 5 uses a predetermined cutoff frequency, here, a noise component of a high band frequency based on a frequency that is 2 to 3 times the recording / reproducing frequency, here I.
The amplifier noise of the V conversion amplifier 3 is removed. The signal from which the noise component has been removed in this way is converted into binarized data by the binarization circuit 6, and MO representing the user data recorded in the user data section 23 of the optical disc 11 is shown.
The signal 12 and the ID signal 13 indicating the address data recorded in the address section 22 are output.

Of these, the ID signal 13 is input to the ID detecting / reading circuit 7, and various position information on the recording / reproducing surface of the optical disk 11, that is, the track number and the sector number corresponding to the radial position of the optical disk 11 are read. These position information is sent to the CPU 9 via the I / O circuit 8.
Is input to the low-pass filter 5 and the cut-off frequency is calculated according to the radial position and the band setting process for the low-pass filter 5 is performed.

In the memory 10, the minimum recording mark length and the recording / reproducing frequency corresponding to the radial position are registered in advance. The CPU 9 reads the minimum recording mark length and the recording / reproducing frequency corresponding to the radial position indicated by the track number and the sector number from the ID detecting / reading circuit 7 from the memory 10, and the corresponding cutoff frequency, for example, the recording / reproducing frequency 2 to 2. Calculate the cutoff frequency of 3 times,
This cutoff frequency is set for the low pass filter 5.

As described above, the low-pass filter 5 whose cut-off frequency can be arbitrarily set is provided in the subsequent stage of the IV conversion amplifier 3, and the cut-off frequency corresponding to the position information detected from the reproduction signal is sequentially supplied to the low-pass filter 5. Since the setting is made, the optimum cutoff frequency according to the radial position of the track being reproduced is quickly set in the low-pass filter 5, and the amplifier noise generated in the IV conversion amplifier 3 is accurately removed. It becomes possible to do.

[0026]

As described above, according to the present invention, the entire recording / reproducing surface of an optical disc is divided into a plurality of regions in the radial direction, the rotation speed of the optical disc is kept constant, and the recording / reproducing frequency is set for each region. When changing and recording / reproducing arbitrary information, the minimum recording mark length in the outer peripheral side area is made larger than the minimum recording mark length in the inner peripheral side area. Therefore, compared with the case where the minimum recording mark length in each area is fixedly set, the S / N ratio is high in all areas of the optical disk without being influenced by the fluctuation of the amplifier noise with respect to the change of the recording / reproducing frequency.
The ratio can be stably obtained, and high reliability is obtained in the recording / reproducing operation.

Further, a low-pass filter which is provided after the amplifier for amplifying the reproduction signal and removes high frequency band noise generated in the amplifier based on an arbitrary cutoff frequency is provided. Since the cutoff frequency corresponding to the position information of the track being played detected from the playback signal is set, the optimum cutoff frequency according to the radial position of the track being played is quickly set in the low-pass filter. This makes it possible to accurately remove the amplifier noise generated by the amplifier.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a recording format of an optical disc by an information processing device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a relationship between an optical disc radius and a recording / reproducing frequency in the ZCAV method.

FIG. 3 is an explanatory diagram showing a relationship between a recording / reproducing frequency and amplifier noise.

FIG. 4 is an explanatory diagram showing the relationship between the minimum recording mark length and the carrier level of a reproduced signal.

FIG. 5 is a block diagram showing a reproduction signal system of the information processing apparatus according to the embodiment of the present invention.

FIG. 6 is an explanatory diagram showing recording units (sectors) provided on the recording / reproducing surface of the optical disc.

FIG. 7 is an explanatory diagram showing a recording format of an optical disc in a conventional ZCAV system.

[Explanation of symbols]

1 ... Optical head, 2 ... Reproduction signal detector, 3 ... IV conversion amplifier, 4 ... Waveform equalization circuit, 5 ... Low-pass filter, 6 ... 2
Thresholding circuit, 7 ... ID detection / reading circuit, 8 ... I / O circuit, 9
... CPU (control means), 10 ... Memory (ROM / RA
M), 11 ... Optical disc, 12 ... MO signal, 13 ... ID
signal.

Claims (2)

[Claims] 1. A desired signal is recorded by irradiating a predetermined track provided on a recording / reproducing surface of an optical disk with a light beam to record a minute mark, and a reproduction signal according to reflected light of the light beam. Has a means for reproducing desired information by detecting the presence or absence of a mark, and divides the entire recording / reproducing surface of the optical disc into a plurality of regions in the radial direction to keep the number of revolutions of the optical disc constant and In an information recording / reproducing apparatus that records / reproduces arbitrary information by changing the recording / reproducing frequency for each area, the minimum recording mark length in the outer peripheral area is compared with the minimum recording mark length in the inner peripheral area of each area. An information recording / reproducing apparatus having a large size. 2. The information recording / reproducing apparatus according to claim 1, which is provided in a stage subsequent to an amplifier for amplifying a reproduced signal and removes noise in a high frequency band generated in the amplifier based on an arbitrary cutoff frequency. An information recording / reproducing apparatus comprising: a filter; and a control means for setting a cutoff frequency corresponding to position information of a track being reproduced detected from a reproduction signal with respect to the low-pass filter.