JPS6142737A - Optical disk device - Google Patents

Abstract

PURPOSE:To obtain the optical disk device which is increased in storage capacity by increasing the bit density without causing any mutual interference of the output waveform of a playback signal even when bit intervals are narrowed down by allowing the waveform of write laser light to have a specific standard energy value at a leading and a trailing edge part. CONSTITUTION:A write signal 22 forms a bit 23 by irradiating an optical disk with laser light 22a having higher energy than readout laser light 22c having low energy. The waveform of the write signal 22 is not rectangular, but held at the 1st energy write signal 22 is not rectangular, but held at the 1st energy standard (22a) for a short time and then decreases monotonously to an energy value of a standard 22b in the middle between the 1st standard and the 2nd standard (22c). Therefore, the bit 23 has a semicircular part as the left half and a part thinner than a semicircle as the right half. Consequently, the output waveform of the playback signal has no mutual interference even when the bit density is increased, so the storage capacity can be increased.

Description

[Detailed Description of the Invention] [Technical Field] Regarding optical disk devices, in particular, pits 6 are formed on an optical disk by full irradiation of high-energy laser beams from an optical head, and low-energy laser beams are formed from the same optical head. The present invention relates to an optical disc device having a configuration for writing and reading information by irradiating laser light and detecting reflected light from bits.

[Prior art]

When writing information onto an optical disk in a conventional writable optical disk device, a high-energy laser beam is focused onto the optical disk using an optical lens and is applied to the optical disk to cause melting or other damage to the storage medium of the optical disk. Information is recorded by forming a hole-like part called a pit by causing an optical state change, and then by irradiating the pit with a low-energy laser for reading and detecting the reflected light. The recorded information is read out in row 5.

The shape of the pit at this time is as shown in Fig. 1 (a) t7t is (b
), it is formed into a circular or oval shape by controlling the waveform of the laser beam for writing.

On the other hand, information is read by detecting the peak point of the output waveform of the reproduced signal in the case of one circular bit, and by detecting the width of the output waveform of the reproduced signal in the case of i oblong pits.

Therefore, in the case of the circular pit illustrated in FIG. 1(a).

When the interval between the pits 3 formed by the write signal 2 becomes smaller than a certain value, the wavelength of the reading laser beam is constant, and therefore the beam diameter is constant, so mutual interference occurs in the reproduction number I 4 (see 4b), this reproduced signal 4
The read information signal 5 obtained by shaping the signal is likely to be an error ratio signal.

Therefore, it has the disadvantage that the distance between the pits cannot be kept below a certain value.

In addition, in the case of the oval pit illustrated in Figure 1 tb),
The semicircular leading and trailing edge portions that form the entire outer shape of the pit 13 (the shape of the elagin becomes irregular (when the storage medium is melted due to heating by laser light, the edge portion is shaped into a geometrically correct half). (It is not circular but has an irregular shape with uneven surfaces.)

The output waveform of the reproduced signal 14 from such a pit 13 is illustrated with a dot as reference numeral 14' in FIG. 1(b):
In other words, - the waveform deviates from the normal position.

If this deviation becomes large, the rise and fall of the readout information signal 15, which has been shaped into a rectangular waveform by shaping the output waveform of the reproduced signal, will not be detected correctly at the regular pulse position of the readout timing pulse 16 (i.e., the width of the readout information signal 15). Therefore, there is a drawback that stable reading of information is not possible.

[Purpose of the invention]

The purpose of the present invention is to improve the drawbacks of the above-mentioned conventional techniques, and
To provide an optical disc device that does not cause mutual interference in the output waveform of reproduced signals even when the pit interval is narrowed, and can therefore increase the pit density and increase the information storage capacity of the same original disc. be.

[Structure of the invention]

In the optical disk manufacturing method of the present invention, pits are formed on the optical disk by irradiating a laser beam of a first energy level from an optical head, and an energy value lower than the energy value of the first energy level is emitted from the optical head. In an optical disc device that writes and reads information by irradiating the optical disc with a laser tip at a second energy level of a value and detecting light reflected from the pit, the laser tip has a second energy level. The signal waveform of the laser beam has a high level first energy value at its leading edge, and has a value intermediate between the first energy value and the second energy level energy value at the trailing edge. and decreases from the first energy value to the second energy value along a curve approximating a quadratic curve or at least one step-like shape, or the signal waveform of the laser beam at the first energy level has a second energy value at its leading edge having an intermediate value between the first energy value and the energy value at the second energy level; and has a first energy value at a high level at its rear edge, and extends from the second energy value to the first energy value along a curve approximating a quadratic curve or at least one step-like shape. It is configured by increasing the

〔Example〕

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to all the drawings showing embodiments.

FIG. 2 shows a write signal waveform according to an embodiment of the present invention.

The shape of the bit on the medium formed thereby, the reproduced signal generated by the reflected light from the bit, the waveform of the read information signal that has been shaped into a rectangular wave, and the t-read timing pulse. It is a drawing.

The write signal 22 of this embodiment shown in FIG. (The pits 23 are formed by irradiating the optical disc with a laser beam of (hereinafter referred to as the first energy level), but the waveform of the write signal 22 at this time is a conventional rectangular wave (see Fig. 1).
, the quadratic curve curve O It has a shape that decreases monotonically along a curve that approximates this. In the figure, reference symbol 2Zd is the level of energy value O? (The same applies to Figures 1 and 3).

The shape of the bit 23 formed by irradiation with laser light having such a cutting signal waveform is dramatically similar to that shown in FIG.
) The shape is different from the conventional circular shape shown in ). In other words, the left hand portion of the bit is approximately semicircular, but the right half is not supplied with enough energy to form a semicircle, so the semicircular shape becomes thinner and thinner, resulting in a shape that approximates the rough triangle shown by reference numeral 23a. becomes.

Therefore, in the waveform of the reproduced signal 24 caused by the reflected light from this oddly shaped bit, the output value in the latter half decreases rapidly compared to the waveform from the conventional circular bit. The second half is a waveform with an asymmetrical shape. When these two pits are close to each other, the mutual interference between the output waveforms of the reproduced signal 24 from these two pits is as follows:
It is smaller than the conventional one (see reference numeral 4b in FIG. 1(a)), as shown in FIG. 2, reference numeral 24b. Therefore, the readout information signal 2 is shaped into a rectangular wave by shaping the reproduced signal 24.
5 becomes an independent rectangular wave corresponding to each of the 92 adjacent bits mentioned above, and a correct read operation is performed, so it is possible to shorten the distance between two bits compared to the conventional method. Therefore, the storage density of information can be increased accordingly.

The waveform of the write signal may be configured not only to decrease along a monotonous curve as shown in FIG. 1M2 but also to decrease along various step-like shapes as shown in FIG. In other words, in FIG. 3(a), the second
Fig. 3 (b) shows a case in which the number decreases sequentially in a stepwise manner with three steps, and Fig. 3 (C) shows a case in which the intermediate part is a special shape that is lower than the final step. In any of these cases, the shape of the bit formed on the medium is very similar to that shown in FIG. 2, and its operation and effect are exactly the same as described above.

Note that all of the above embodiments show cases where the write signal waveform has a high level energy value at the leading edge and an intermediate level energy value at the trailing edge, but this relationship can be reversed. Let me.

An energy value of intermediate magnitude at the leading edge.

The energy value is at a high level at the trailing edge, and 2
By configuring the structure to increase monotonically along a curve of Effects can be obtained.

〔Effect of the invention〕

As explained in detail above, by using the optical disk device of the present invention, the bit spacing on the medium can be narrowed compared to the conventional one, so that the information storage capacity can be reduced using an optical disk of the same size. This has the effect that a large optical disk device can be obtained.

[Brief explanation of drawings]

FIG. 1(a) and FIG. 1(b) show convolution signals of a conventional optical disk device when forming one circular and oval bits,
FIG. 2 is a waveform diagram of the write signal, read information signal, etc. of the first embodiment of the present invention, and FIGS. 3(a), (b), and (C) are waveform diagrams of the read information signal, etc. Second,
It is a waveform diagram of the write signal of the third and fourth embodiments. In fig. 2...Write signal, 3...Pit, 4
...Reproduction signal, 5 ...Read information signal, 12 ...Write signal, 13 ...Bit, 14 ...Reproduction signal, 15 ... Read information signal, 16 ... Read timing node, 22 ... Write signal, 23 ... Pi on medium, ), 24 ... ...Reproduction signal, 25...
...Read information signal, 32, 42.52...
write signal. Daimin Buno V Luss -11 ml /I! 1

Claims (1)

[Claims] forming pits on the optical disk by irradiating laser light of a first energy level from the optical head, and laser light of a second energy level having an energy value lower than the energy value of the first energy level from the optical head; In an optical disk device that writes and reads information by irradiating the laser beam onto the optical disk and detecting the reflected light from the pit, the signal waveform of the laser beam having the first energy level has a high level at its leading edge. and has a second energy value at its trailing edge having a value intermediate between the energy value of the first energy level and the energy value of the second energy level; The signal waveform of the laser light at the first energy level decreases from the energy value to the second energy value along a curve approximating a quadratic curve or at least one step-like shape, or a second energy value at its leading edge having a value intermediate between the energy values of said first energy level and said second energy level; and a first energy value of a higher level at its trailing edge. an optical disc device, wherein the energy value increases from the second energy value to the first energy value along a curve approximating a quadratic curve or at least one step-like shape.