JPH06168454A - Optical recording medium and optical recording method - Google Patents

Abstract

(57) [Abstract] [Purpose] In the method of using a short wavelength laser for recording and erasing in order to realize high density recording, the output decreases as the wavelength of the laser shortens and sufficient power for recording and erasing is obtained. Solve the problem of not being able to. [Structure] In an optical recording medium for recording or erasing by converging a laser, pits are formed in advance over the entire surface at intervals corresponding to a clock frequency. This pit should be laser-readable by a method such as changing the reflectance from a place other than the pit. This is read by a short-wavelength laser, a clock of that frequency is created, and a long-wavelength laser, which is changed according to information, is applied to the optical recording medium in synchronization with the clock.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the field of optical recording technology for recording or erasing by converging a laser, and more particularly to an optical recording medium and an optical recording method effective for high density recording.

[0002]

2. Description of the Related Art In recent years,
There is an increasing need for high density, large capacity memory that can rewrite information. Among them, magneto-optical recording has been actively developed because it is rewritable, and some of them are already on the market. Currently, as one of the high performance of magneto-optical recording, researches for improving recording density are being actively conducted. There is a method of using a short wavelength laser for recording and erasing as one of the means for realizing high density recording, but the output decreases as the wavelength of the laser shortens and sufficient power for recording and erasing cannot be obtained. There was a problem.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical recording medium and an optical recording method, which solve the above problems in the prior art, enable high density recording, and can perform laser irradiation with sufficient power. To do.

[0004]

In order to achieve the above object, according to the invention of claim 1, in an optical recording medium for recording or erasing by converging a laser, laser reading is performed on the optical recording medium. An optical recording medium is provided in which pits that can be taken out are formed in advance over the entire surface at intervals corresponding to a clock frequency. Further, according to the invention of claim 2, in an optical recording medium for recording or erasing by converging a laser, laser-readable pits are pre-printed on the optical recording medium at intervals corresponding to a clock frequency. An optical recording medium characterized by being formatted is provided. Further, according to the invention of claim 3, in a sample servo type optical recording medium for recording or erasing by converging a laser, pre-pits are formed at intervals corresponding to a clock frequency. A recording medium is provided. According to the invention of claim 4, when recording or erasing is performed using the optical recording medium of claim 1, a pit previously formed on the optical recording medium is read by a preceding laser, There is provided an optical recording method characterized in that a write clock is created at a frequency, and information is written by irradiating a pit with a pulse that is changed according to information by a laser that follows, in synchronization with the write clock. . Further, claim 5
According to the present invention, when recording or erasing is performed using the optical recording medium according to claim 2 or 3, pits formed in advance on the optical recording medium are read by the preceding laser, and at the frequency thereof. There is provided an optical recording method characterized in that a write clock is created and information is written by irradiating a pulse which is changed according to information with a laser following the light in synchronization with the write clock.

[0005]

In the present invention, since high-density pits are formed in advance on the optical recording medium, a long-wavelength laser is read by a short-wavelength laser, a clock of that frequency is created, and the wavelength is changed according to information. By irradiating the optical recording medium in synchronism with the clock, the above-mentioned problem of insufficient power is solved, and recording and erasing can be performed with sufficient power and high density, and the above-mentioned problems are solved.

[0006]

The present invention will be described in detail below. FIG. 1 is a diagram schematically showing a recording track T of an optical recording medium according to the present invention. This optical recording medium is for recording or erasing by converging a laser, and pits P are formed in advance over the entire surface at intervals corresponding to the clock frequency. The pit P can be read by a laser by a method such as changing the reflectance from a place other than the pit P. Here, for example, as a method of changing the reflectance between the pits P and other portions, there is a method of changing the substrate surface roughness at both portions, dividing the substrate surface into a crystalline portion and an amorphous portion, or the like. is there. The method of forming the pits P is not limited to the above method, as long as the reading of the recording mark can be performed by a method different from that of reading the recording mark, in addition to changing the reflectance. When the diameter of these pits P is r and the pitch is d, when r and d are small, that is, when high density recording is performed, recording,
Effective in erasing. Especially r ≦ 0.3 μm,
When d ≦ 0.6 μm, a remarkable effect is exhibited.

Next, a recording and erasing method using the above optical recording medium will be described. Generally, since the reading resolution is almost determined by the wavelength of the light source and the numerical aperture of the lens, a laser with a wavelength shorter than 600 nm is suitable for reading pits of the above size. Therefore, in the present invention, 600
A pit is read by a short wavelength laser having a wavelength shorter than nm, and a clock signal (write clock) is generated at that frequency as shown in FIG. In this case, the laser output does not need to be large and only a few mW is sufficient because it is only for reading.

Next, as shown in FIGS. 3A to 3C, a laser having a wavelength of 600 nm or more, which is changed according to the information to be recorded, is applied to the optical recording medium in synchronization with the clock signal. FIG. 3C shows an example of a pulse waveform of a laser for writing information, and it may be different depending on the recording method and the type of medium. It is desirable that the pulse width be as short as several nsec to 10 nsec. For recording and erasing, a long-wavelength laser with an output of at least several tens of mW is preferable, and the wavelength is 600 nm.
The above is desirable.

When the above operation is performed, the marks corresponding to the information "1" and "0" are written on the pit P formed in advance as shown in FIG. 3 (d). In this way, by reading high density pits with a short wavelength laser and recording and erasing with a long wavelength laser using the frequency as a write clock, recording and erasing can be performed with sufficient output despite high density recording. Like It should be noted that in FIG. 3D, black pits represent marks corresponding to "1" and white pits represent marks corresponding to "0".

In the above description, the pits are formed in advance on the entire surface at intervals corresponding to the clock frequency. However, according to the present invention, these pits may be pre-formatted. In this case, the preformatted portion is read by a short wavelength laser to create a write clock. In this case, the laser output does not need to be large and only a few mW is sufficient since only reading is required. Information is written by irradiating a pulse changed according to information with a long wavelength laser in synchronization with a clock. As a result, the same effect as above can be obtained.

The present invention can also be applied to the sample servo system. Also in this case, pre-pits are formed on the optical recording medium at intervals corresponding to the clock frequency. Then, the pre-pit is read with a short wavelength laser to create a write clock. Also in this case, the laser output does not need to be large and only a few mW is sufficient since only reading is required. Information is written by irradiating a pulse changed according to information with a long wavelength laser in synchronization with a clock. As a result, the same effect as above can be obtained.

[0012]

As described above, according to the present invention, since the pits are formed in advance on the optical recording medium with a high density, the pits are read by a short wavelength laser, a clock of that frequency is created, and the length is changed according to the information. By irradiating the optical recording medium with a laser having a wavelength in synchronization with the clock, a sufficient laser output can be obtained and high density recording and erasing can be realized.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of pits provided on a track of an optical recording medium of the present invention.

FIG. 2 is an explanatory diagram of a write clock created by reading out the pits.

3A is an explanatory diagram of information to be recorded, FIG. 3B is a write clock, FIG. 3C is a laser waveform, and FIG.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Motoharu Tanaka 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (72) Masaetsu Takahashi 1-3-6 Nakamagome, Ota-ku, Tokyo Shares Inside Ricoh Company (72) Inventor Koji Deguchi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company, Ltd.

Claims (5)

[Claims] 1. In an optical recording medium for recording or erasing by converging a laser, laser-readable pits are formed in advance over the entire surface of the optical recording medium at intervals corresponding to a clock frequency. An optical recording medium characterized by the above. 2. An optical recording medium for recording or erasing by converging a laser, wherein laser-readable pits are pre-formatted on the optical recording medium at intervals corresponding to a clock frequency. Characteristic optical recording medium. 3. An optical recording medium of a sample servo system for recording or erasing by converging a laser, wherein prepits are formed at intervals corresponding to a clock frequency. 4. When recording or erasing is performed using the optical recording medium according to claim 1, a pit previously formed in the optical recording medium is read by a preceding laser, and a write clock is generated at the frequency. An optical recording method is characterized in that information is written by irradiating a pit with a pulse that is changed according to information by a subsequent laser in synchronization with the write clock. 5. When recording or erasing by using the optical recording medium according to claim 2 or 3, a pit previously formed on the optical recording medium is read by a preceding laser and written at the frequency. An optical recording method, wherein a clock is created, and information is written by irradiating a pulse which is changed according to information with a laser following the laser in synchronization with the write clock.