JPH0325727A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To improve the symmetry of an eye pattern at the time of radiating laser light with power at constant level in the case of reproducing a recorded signal by providing a signal width detection means for detecting the width of a recorded signal and a level conversion means based on the information. CONSTITUTION:When an EFM signal at the constant level is outputted from an EFM encoder 1, a laser driving pulse having a width corresponding to the width of the EFM signal and a level in accordance with setting is outputted by the detected signal of a pulse width detector 3 in a level converter 2. A laser driving circuit 4 makes a semiconductor laser 5 radiate the laser light by a time in accordance with the width of the pulse to form a recording part 6. Therefore, by irradiating the recording part 6 at the time of reproducing with the laser light with the constant power smaller than the power at the time of recording, a reproduced signal at a level in accordance with the laser power is obtained and the asymmetry of the eye pattern reproduced at the level in accordance with the cycle of the EFM signal is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical information recording and reproducing device that optically records and reproduces signals obtained by digitizing analog signals such as audio and visual signals, and digital data such as computers. It is related to.

[Conventional technology]

Conventionally, optical discs that perform recording and reproduction using the difference in reflectance due to laser beam irradiation have been used, for example, when recording an EFM signal on the disc, as shown in FIG.
When the FM signal is at a high level, by irradiating the optical disc with a laser beam of a constant output, a recorded area having a lower light reflectance than the area not irradiated with the laser beam is formed on the optical disc. To read the EFM signal recorded in this recording section, when the optical disc is irradiated with a laser beam of a certain level that cannot be recorded, light with a lower intensity than the area not irradiated with the laser beam returns from the recording section, so this light A reproduced signal corresponding to the intensity can be obtained.

[Problem to be solved by the invention]

However, in the above-mentioned conventional method of recording using a laser beam with a constant output, the portion of the reproduced signal corresponding to the recorded portion is aligned at a constant level, resulting in poor symmetry of the eye pattern. Since the asymmetry of the eye pattern waveform may lead to deterioration of recording and reproducing characteristics, it has been desired to improve the symmetry of the eye pattern in order to solve such problems.

[Means to solve the problem]

In order to solve the above-mentioned problems, an optical information recording/reproducing apparatus according to the present invention includes a laser light source that irradiates a disk with laser light and a driving means that drives the laser light source, and emits a plurality of pulses of a constant period. In an optical information recording and reproducing device that records information by irradiating a disk with a laser beam for a time corresponding to the width of the signal it has, and forming a recording area whose light reflectance is different from the area not irradiated with the laser beam, recording is performed. A signal width detection means detects the width of the signal, and the input recording signal is adjusted to a level set according to the width of the recording signal based on the information on the width of the recording signal detected by the signal width detection means. and level converting means for converting the signal and supplying the level-converted signal to the driving means.

[For production]

According to the above configuration, based on the information on the width of the recording signal detected by the signal width detection means, the level conversion means converts the input recording signal to a level corresponding to the width. The driving means is supplied with a recording signal whose level has been converted, and drives the laser light source in accordance with the level of this recording signal. Therefore, the laser light source emits laser light with a power that corresponds to the level of the recording signal supplied to the driving means.

For this reason, for example, EFM on compact discs
When recording a signal that has multiple pulses with a constant period, the recording area is formed by irradiating the disk with a laser beam with a power that corresponds to the width of the recording signal, so the optical reflectance of the recording area is It varies depending on the power of the laser beam mentioned above. Therefore, when reproducing a recorded signal, if the recording section is irradiated with a laser beam at a certain level of power, the portion of the reproduction signal corresponding to the recording section will have a level corresponding to the power of the laser beam at the time of recording. The symmetry of the eye pattern can be improved.

〔Example〕

An embodiment in which the present invention is applied to a write-once compact disc will be described below with reference to FIGS. 1 to 3.

As shown in FIG. 1, in the optical information recording and reproducing apparatus, an input signal supplied from a signal source (not shown) is inputted to a level converter 2 and a pulse width detector 3 via an FM encoder 1. The signal from the level converter 2 is input to a laser drive circuit 4, and the drive signal from this laser drive circuit 4 is supplied to a semiconductor laser 5.

On the other hand, a detection signal is supplied from the pulse width detector 3 to the level converter 2 as required.

The EFM encoder 1 is a circuit that modulates an input signal such as a digitized analog signal such as an audio signal or a video signal, or digital data handled by a computer, etc., into an EFM signal. A level converter 2 serving as a level converting means converts the input EFM signal into a laser beam having a width and a level according to the width of the EFM signal, in other words, the period of the pulse of the EFM signal, according to the detection signal of the pulse width detector 3. This is a circuit that converts it into drive pulses.

The pulse width detector 3, which serves as signal width detection means, recognizes the frequency of the EFM signal by detecting the width Tw (shown in FIG. 2) of the input EFM signal, and outputs a detection signal according to the period. This is a circuit that outputs. The laser drive circuit 4 serving as a driving means is a circuit that drives the semiconductor laser 5 with an output corresponding to the laser drive pulse of the level converter 2. A semiconductor laser 5 serving as a laser light source is configured to irradiate a disk (not shown) with laser light to record and reproduce signals.

The EFM signal is composed of pulses having nine types of periods from 3T to IIT. Therefore, in the level converter 2, the level 1 of the laser drive pulse shown in FIG. 2 is set to three types depending on the period of the EFM signal. For example, the level H of each laser drive pulse is set to be the minimum for EFM signals with periods of 3T and 4T, and for EFM signals with periods of 5 to 7T.
In the case of an FM signal, it is set to a value slightly higher than the minimum level, and in the case of an EFM signal whose cycle is from 8T to IIT, it is set to be the maximum.

To record an EFM signal on a disc using the recording device configured as described above, when the EFM encoder 1 outputs an EFM signal of a constant level as shown in FIG. 2, the detection signal of the pulse width detector 3 outputs a laser drive pulse having a width corresponding to the width T of the EFM signal and a level H corresponding to the above setting. Then, the laser drive circuit 4 drives the semiconductor laser 5 for a time corresponding to the width of the laser drive pulse with an output corresponding to the level I1 of the laser drive pulse. The disk is irradiated with laser light emitted from the semiconductor laser 5, and a recording section 6 is formed in that area.

The recording section 6 reproduces the EFM signal recorded in the recording section 6 because the reflectance of the irradiated laser beam is reduced when the power of the irradiated laser beam is large. In this case, by irradiating the recording section 6 with a laser beam having a constant power lower than the power of the laser beam during recording,
A reproduced signal having a level corresponding to the irradiated laser power as shown in FIG. 3 is obtained. Therefore, this reproduced signal is EFM
The signal is reproduced at a level corresponding to the period of the signal, and the asymmetry of the eye pattern is improved.

〔Effect of the invention〕

As described above, the optical information recording and reproducing apparatus according to the present invention includes a laser light source that irradiates a laser beam onto a disk, and a driving means that drives the laser light source, and has a width of a signal having a plurality of pulses with a constant period. In an optical information recording/reproducing device that records information by irradiating the disc with a laser beam for a corresponding period of time and detecting the recorded area where the light reflectance is different from the area not irradiated with the laser beam, the width of the recording signal is detected. and converts the input recording signal to a level set in advance according to the width of the recording signal based on the information on the width of the recording signal detected by the signal width detection means, and converts the input recording signal to a level set in advance according to the width of the recording signal. and level converting means for supplying the signal to the driving means.

As a result, a recording section is formed by irradiating the disk with a laser beam using a laser power corresponding to the width of the signal to be recorded, so that the recording section has a different light reflectance depending on the laser power. Therefore, during playback, if the recording section is irradiated with laser light at a certain level of laser power, the portion of the playback signal corresponding to the recording section will have a level corresponding to the power of the laser light during recording, resulting in an eye pattern. The symmetry of can be improved. Therefore, it is possible to easily improve the recording and reproducing characteristics.

FIG. 1 is a block diagram showing the structure of the main parts of an optical information recording/reproducing device.

FIG. 2 is an explanatory diagram showing the relationship between the EFM signal and the laser drive pulse.

FIG. 3 is an explanatory diagram showing a laser drive pulse, a recording section, and a reproduction signal according to an EFM signal.

FIG. 4 shows a conventional example, and is an explanatory diagram showing a recording section and a reproduction signal according to an EFM signal.

2 is a level converter (level converting means), 3 is a pulse width detector (signal width detecting means), 4 is a laser drive circuit (driving means), and 5 is a semiconductor laser (laser light source).

Claims (1)

[Claims] 1. A laser light source that irradiates a disk with laser light and a driving means that drives the laser light source, and irradiates the disk with laser light for a time corresponding to the width of a signal having a plurality of pulses with a constant period. In an optical information recording and reproducing device that records information by irradiating a laser beam onto a laser beam and forming a recording area having a different light reflectance from an area that is not irradiated with a laser beam, there is provided a signal width detection means for detecting the width of a recorded signal; Based on the information on the width of the recording signal detected by the detection means,
An optical information recording and reproducing device characterized by comprising a level converting means for converting an input recording signal to a level set in advance according to the width of the recording signal and supplying the level-converted signal to a driving means. Device.