JPH0222451B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical recording and reproducing method that compensates for variations in recording position accuracy of optical recording materials using a laser beam scanning method.

A part of the optical recording layer of an optical recording material is volatilized, deformed, or has its reflectance changed by irradiation with a laser beam, and as a result, recording is performed based on the difference in light reflectance or transmittance, or the recording obtained in this way is performed. The optical recording and reproducing method itself is already known in which information is reproduced by irradiating the optical recording layer of a recorded optical recording material with a laser beam. Optical recording and reproducing methods can reproduce information without contact, and have the advantage of higher recording density than other recording and reproducing methods. However, in the optical recording and reproducing method, since information is contained within a track of about 1 micron width at most, it is necessary to accurately detect the recording position of the information and to scan and reproduce the information without deviating from the track. Optical disks are known as a typical optical recording material, but
On optical discs, information is recorded in a spiral or concentric pattern like the sound grooves of a record, and therefore, if the positional accuracy of the center is maintained to a certain degree, information can be recorded from the periphery to the center of the optical disc. Tracks can be detected by scanning almost in a straight line.
Tracking is relatively easy, and deviations in the drive of the optical disk are periodic and can be dealt with. Such optical disks have a large storage capacity and can be accessed randomly, so they are used in the fields of image, audio, and computer storage media. on the other hand,
Since the optical recording and reproducing method has a high recording density, it can also be used as a small and portable recording medium.For example, magnetic methods are currently used for magnetic cards, information cards, product tags, English cards, etc. When used in various fields, it is possible to record and reproduce more information on a recording medium of the same size. However, when these recording media are used commercially, there are variations in the dimensional accuracy of the recording media, the accuracy of the recording position, and the running accuracy of the recording media, and the recording on these recording media is not linear. Because of this, a drive device for precise movement is required to detect and follow the recorded portion, and the drive bias is random, making playback particularly difficult compared to optical disks. For example, when a magnetic card is replaced with an optical recording/playback type card, the dimensional accuracy is about ±50μ to ±100μ, and considering that the diameter of the laser beam is about 1μ, the recording part is Measures must be taken for detection and follow-up. In order to detect and follow the recording section, optical recording lines and mechanically processed grooves are prepared in advance for guidance, and these guiding lines and grooves are detected and followed optically and mechanically. An attempt has been made to record the original information at a position parallel to these lines and grooves, keeping a certain distance therebetween, and to facilitate reproduction. However, provision of such guide grooves and lines and means for detecting these are necessary in addition to recording and reproducing means, and complexity is unavoidable.

The inventor of the present invention has conducted various studies in order to eliminate the drawbacks of the above-mentioned conventional techniques, and has found that the above-mentioned recording medium that records information in a straight line is required to have a high recording density in the straight direction. On the other hand,
The recording density in the width direction is often relatively unproblematic, so if you expand the recording in the width direction, the recording density in the linear direction, and by extension the recording density of the recording medium itself, will not decrease, and on the contrary, playback will be affected. They discovered that it is possible to absorb variations in the running accuracy of time, and that information can be easily reproduced by vibrating the laser beam perpendicular to the scanning direction when reproducing a recording medium on which information is recorded in this way. The present invention was also achieved by discovering the following.

That is, the present invention provides an optical recording and reproducing method in which recording and reproducing is performed by focusing and scanning a laser beam on an optical recording layer of an optical recording material, in which the laser beam is vibrated in a direction perpendicular to the scanning direction during recording. The gist of this optical recording and reproducing method is to form pits while enlarging the recording width, and to scan while vibrating in a direction perpendicular to the scanning direction during reproduction.

The present invention will be explained in detail below.

As the optical recording material used in the present invention, any material can be used as long as a portion of the optical recording layer produces a difference in light reflectance or transmittance when irradiated with laser light. These optical recording materials can be used, for example, as an optical recording layer on a smooth, heat-resistant substrate.
Examples include those in which low melting point metals such as Te, Bi, Sn, and In are provided in the form of a thin film, and those in which two different types of metals are laminated.

Recording on these optical recording materials is carried out using conventional methods with some further modifications.
For example, as shown in FIG. 1, a laser beam emitted from a laser light source 1 is reflected by a fixed mirror 2 and condensed by a condenser lens 3 to form an optical recording material 4.
Ordinary recording can be performed by irradiating the light onto the surface of the optical recording material.As shown in FIG. 1/4 wavelength plate 8
The light can then be introduced into a photodiode 10 by a polarizing beam splitter 9 for reading.

In the above recording method, in the present invention, in particular, recording is performed in a straight line while relatively linearly moving the laser beam and the optical recording material, and the recording width is moved in a direction perpendicular to the length direction of the straight line. Expand. Enlargement can be done in various ways, but if it is done in the same way as the reproduction described later, it is best to vibrate the laser beam in the width direction, and the vibration is the first
Instead of mechanically vibrating the fixed mirror indicated by reference numeral 2 in the figure, or using TeO ₂ , instead of using a fixed mirror,
This can be accomplished by using a crystal such as LiNbO ₃ (called an "acousto-optic polarizer"), generating ultrasonic waves within the crystal, and diffracting laser light. The frequency, amplitude, etc. of vibration vary depending on the manufacturing precision of the optical recording material, the diameter of the laser beam, and other conditions, so it cannot be generalized, but if it is for the above-mentioned recording medium, the dimensional accuracy of the optical recording material is ±50μ~
±100μ, the diameter of the focused laser beam is 1μ, and the scanning speed of the optical recording material is 100mm/sec.
If so, the frequency of vibration is, for example, 100KHz or more,
The amplitude is at least 100μ to 200μ on the optical recording material. Regarding the conditions and vibrations above, the above values are just examples and are not restrictive.
The laser beam diameter is usually about 0.5μ to 1.5μ,
If the diameter of the laser beam is increased, the accuracy of the shape of each pit will deteriorate, so a narrower diameter is preferable. The length of each pit in the linear scanning direction is usually about 5μ to 50μ. Further, the scanning speed of the optical recording material may be based on the current scanning speed of magnetic cards (80 mm/sec), but is not limited to this. The frequency of the laser beam during scanning is determined by dividing the scanning speed of the optical recording material by the diameter of the laser beam, and the amplitude should be sufficient to cover the range of variations in the dimensions of the optical recording material.

In order to reproduce the optical recording material that has been optically recorded in this way, a known method as shown in FIG. Therefore, it is only necessary to add vibration in a direction perpendicular to the scanning direction, and the frequency and amplitude of the vibration should be the same as in recording, but if possible, the amplitude should be slightly larger.

Note that when reproducing data while vibrating the laser beam in this way, the laser beam often scans with a slight deviation from the recorded pit, and if the laser beam is misaligned, recording and playback will normally be performed using ON-OFF signals of 0 and 1. Since what should be detected is detected as a smaller signal corresponding to the deviation, such as 0 and 0.5, a logic circuit may be added as appropriate to restore the original 0 and 1. Further, by adding such a logic circuit, even if there is a slight scratch on the recorded portion, it is possible to reproduce the scratch as long as the scratch is narrower than the width of the recording.

Since the present invention has the above-described configuration, it is easy to detect a recording track during optical recording and reproduction, and the reproduction head can easily follow the recording track.
Even if there are manufacturing variations in optical recording and reproducing recording media, reproducing can be performed reliably, and furthermore, vibrating the laser beam itself can be easily done using a known technique, and the method of the present invention Reliability can be ensured when using a recording medium with high recording density.

[Brief explanation of drawings]

FIGS. 1 and 2 are explanatory diagrams showing a conventional recording and reproducing method using laser light. 1, 5... Laser light source, 2, 6... Fixed mirror, 3, 7... Condensing lens, 4... Optical recording material, 8... 1/4 wavelength plate, 9... Polarizing beam splitter, 10 ...Photodiode.

Claims (1)

[Claims] 1. In an optical recording and reproducing method in which recording and reproducing is performed by concentrating a laser beam on the optical recording layer of an optical recording material and scanning it, the recording width is changed by vibrating the laser beam in a direction perpendicular to the scanning direction during recording. An optical recording and reproducing method characterized in that pits are formed while enlarging the pits, and further, during reproduction, scanning is performed while vibrating in a direction perpendicular to the scanning direction.