JPS61271627A - Optical disc - Google Patents

Abstract

PURPOSE:To add a write function based on a pit string provided in advance by irradiating a laser beam modulated by optional information to a region between pit strings on an optical disc face so as to make the 2nd recording pit string. CONSTITUTION:Reproducing only pit strings 11 having an interval of t2=2.5-3.5mum are provided on one side of a transparent resin base 1. Onto the face of a flat region 12, for example, a Te group optomagnetic medium layer 3 is vapor-deposited by a thickness of several tens-several thousands A. Information is read as to pits 11 by a conventional method. The laser beam modulated based on optional recording information is irradiated to the region 12 from the same direction A to form recording pits 14 onto the layer 3. In this case, two auxiliary beams are used for the tracking servo based on the reproduction only pit strings 11. The pits 14 are read by the same method as that for the reproduction only pits and tracked by the same method as that at recording. Through the constitution above, no crosstalk at reproduction takes place, reproduction/recording are attained by the same optical head and the device is simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention improves the structure of an optical disc that is normally made only for playback, so that a writing function can be added to it.

2. Description of the Related Art Currently, there are ten so-called compact discs (CDs) on the market, which are read-only optical discs on which audio information is recorded. This compact disc can be used as a burner to store image information, a variety of digital data, or a computer external memo IJ (CD).
-ROM) is being considered.

In particular, its practical application is attracting attention as it is a non-contact memory and has a large capacity as an ambidextrous memory.

This type of compact disc has the structure shown in Fig. 2 as is well known, but all of them are made of a master, mother, and stamper in that order. P
The substrate is made by injection molding using a transparent resin such as MMA (polymethyl methacrylate).

In FIG. 2, 1d is an injection molded substrate made of transparent resin such as polycarbonate, and 11 is a bit representing predetermined information such as audio or data. Pi 1
-11 are connected in a spiral pattern to form a row like the grooves on an ordinary audio record. An aluminum reflective film 2 is formed on the outside of the surface on which the bits 11 are formed, and a laser beam during reading is transmitted and irradiated from the opposite surface 13 as indicated by arrow A. The reflected light changes depending on the presence or absence of the bit 11, but its intensity is read and converted into an electrical signal to reproduce predetermined information.

Problems to be Solved by the Invention Conventional compact discs in which bit strings are injection molded in advance can only be used for playback purposes. If it is to be used as an external memory for a personal computer in the future, its uses will be further expanded if it is not only used as a ROM but also has additional write and rewritable functions.

Means for Solving the Problem The present invention improves an optical disk in which a bit string representing predetermined information is formed in advance on one side by injection molding a transparent resin, and the conventional reflection plate is formed on that surface. An optical recording medium layer is formed instead of the film, and a second recording bit string is formed by irradiating a region provided between adjacent bit strings with a laser beam modulated with arbitrary information. This makes it possible to perform tracking servo based on the bit string.

According to the optical disc of the present invention, the formation areas of the read-only bit string, that is, the read-only track, and the recording track are made different, so that even if the frequencies of both trunks are close, there is no crosstalk and they can be completely separated as separate signals. It is something. Tracking servo during recording can be performed based on a reproduction-only bit string, so there is no need to prepare special tracking grooves in advance, making disk processing simple and easy to manufacture.

Embodiments Examples of the present invention will be explained below with reference to the drawings. FIG. 1 is a partially cutaway perspective view showing the structure of the optical disc of the present invention. Note that the same parts as in the conventional structure shown in FIG. 2 are designated by the same reference numerals.

A read-only bit string 11 formed on one side of the substrate 1.
The pitch t2 of No. 11 is selected to be 2.5 to 3.5 μm and injection molding is performed. The conventional pitch t is 1.6 μm, and the distance is set larger than this. By doing so, a flat area 12 is formed. Instead of forming an aluminum reflective film on the surface on which the bit string 11 is formed, the optical recording medium layer 3 is formed here with a thickness of several 10 to several 1000 λ by a vapor deposition method, a sputtering method, a spin code, or the like.

As this recording medium layer 3, for example, Te-based, organic-based, magneto-optical media, etc. are used.

Information on the read-only bits 11 can be read from the disc produced as described above using the same method as in the past. Next, the area 12 is irradiated from the same direction A with a laser beam modulated based on arbitrary recording information. Then, recording bits 14 are sequentially formed in corresponding portions of the recording medium layer 3 according to the laser beam.

In this case, tracking servo is performed using a so-called three-beam method using two auxiliary beams with a read-only bit string as a reference.

Further, the reading operation for the bit 14 formed in the area 12 is performed in the same manner as in the case of the read-only bit 11, and the tracking is performed in the same manner as during recording.

As an experimental example, recording and reproduction were performed using a semiconductor laser beam with a wavelength of 780 to 830 nm using an optical head with an objective lens of NA: 0.5 to 0.6, but good signals without crosstalk were obtained. Obtained.

In the above-mentioned embodiment, an optical recording medium in which writing is performed only with a laser beam has been described, but this invention performs recording with a magnetic field and a laser beam as in magneto-optical recording.
It goes without saying that erasable items are also applicable.

Further, various shapes of the post-recorded bit 14 can be considered, such as unevenness, bulge, presence or absence of a recording medium layer, change in refraction or reflectance, etc., but any optical change that can be detected by readout light can be applied.

Effects of the Invention According to the present invention, recording bits can be arbitrarily provided in addition to the reproduction-only bits provided in advance, but crosstalk does not occur during each reproduction, and the usability of the optical disc can be expanded. can. In addition, the same optical head can be used to read out read-only bits and to provide recording bits, which simplifies the device.
It is also suitable for downsizing.

[Brief explanation of drawings]

FIG. 1 is a cutaway perspective view showing the structure of an optical disk according to an embodiment of the present invention, and FIG. 2 is a cutaway perspective view showing the structure of a conventional optical disk. 1... Transparent resin substrate, 11... Bit, 3... Optical recording medium layer, 12... Recording area between bit strings.

Claims (1)

[Claims] An optical disc in which bit strings representing predetermined information are formed in advance on one surface by injection molding of transparent resin, and an optical recording medium layer is formed on the surface instead of a reflective film, and between the adjacent bit strings. It is possible to form a second recording bit string by irradiating a region provided with a laser beam modulated with arbitrary information, and to perform tracking servo based on the previously formed bit string. An optical disc featuring