JPH0218716A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To decrease the fluctuation in percentage modulation even if a prepit signal is reproduced without applying track servo thereto and to facilitate information reproduction by forming prepit arrays at the pitch smaller than the specific size of the pitch of the prepit arrays to be reproduced by applying the tracking servo thereto. CONSTITUTION:The prepits to provide modulation to the intensity of reflected light or transmitted light is provided to form the prepit arrays where the prepits line up in the scanning direction of focused light. The region where the prepit arrays line up at the specified pitch is provided and the region where the prepit arrays line up at the pitch <=7/10 the pitch is provided. The fluctuation in the amplitude of the prepit signal reproduced without applying the track servo to the control area of the optical disk is substantially eliminated and the value of the percentage modulation is controlled to the specified value. The information is thus effectively reproduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] [Prior Art] An optical information recording medium (hereinafter referred to as an optical disk) is a removable storage medium having a capacity several tens of times that of a magnetic disk.

There are small holes (hereinafter referred to as pre-pits) on the optical disk that modulate the reflected or transmitted light of the light irradiated there due to irregularities or differences in reflectance, and are used to cut the focused light into tracks and scan it. A guide groove is formed. Optical information recording devices use a focus servo that focuses focused light on the recording surface of an optical disc, and a track servo that controls the position of the focused light so that it does not deviate from the center of the focused light on the guide groove, between the guide grooves, or on the pre-pit row. Thus, the pre-pit row can be scanned with focused light.

[Problems to be Solved by the Invention] Addresses and control information are often recorded in advance by manufacturers in the form of pre-pits.

Addresses are reproduced by applying track servo, but control information is reproduced in some cases by applying track servo and in others without applying track servo.

If control information for playback without applying track servo is recorded in a common format, it is possible to obtain control information for optical discs with different tracking methods, sector formats, etc. before applying track servo. In the area where control information is recorded for playback without applying the track servo (hereinafter referred to as the "control area"), since the trunk servo is not applied, no guide groove is provided, and the prepit row is lined up in the scanning direction of the focused light. It consists only of These pre-pit strings are often recorded with the same modulation over dozens to hundreds of trunks, forming a control area similar to a barcode. When the pre-pits are made of irregularities on the reflective surface, the intensity of the reflected light is small when the focus of the focused light is on the pre-pits, and the intensity of the reflected light is small when the focus is outside the pre-pits and illuminates a flat surface. The intensity of becomes larger. It is possible to reproduce information using a prepit signal that utilizes the modulation of this reflected light, but if you try to reproduce this prepit signal without changing the trunk servo, there is a problem that it does not always work. When reproducing the control area, since no track servo is applied, the focused light may not necessarily be irradiating the pre-pit rows, but may be irradiating between the pre-pit rows. Since the area between the pre-pit rows is a flat surface, the amount of reflected light continues to be large while the focused light is scanning there, so the degree of modulation of the amount of reflected light becomes extremely small.1,5a On the other hand, the focused light When scanning on a column (-), the modulation degree becomes large.Therefore, there is a problem in that the modulation degree of the pre-pit signal fluctuates greatly and it is extremely difficult to obtain control information from this.

The present invention is intended to solve these problems, and its purpose is to provide an optical information recording system in which the degree of modulation changes little even when pre-pit signals are reproduced without applying a track servo, and information can be easily reproduced. It lies in providing the medium.

[Means for Solving the Problems] The optical information recording medium of the present invention has prepits that modulate the intensity of reflected light or transmitted light, and has a prepit row in which the prepits are arranged in the scanning direction of focused light. death,
It is characterized in that it has a region where prepit rows are arranged at a constant pitch, and has a region where prepit rows are arranged at a pitch of 7/10 or less of the pitch.

[Example] Hereinafter, the present invention will be described in detail based on examples.

FIG. 1 shows the arrangement of pre-pits in the control area of the optical disc of the present invention. In contrast, FIG. 2 shows a layout diagram of pre-pits in the control area of a conventional optical disc. Compared to the arrangement of the prepits 201 in the control area of a conventional optical disc, the arrangement of the prepits 101 in the control area of the optical disc of the present invention is dense in the direction perpendicular to the scanning direction of the focused light. In conventional optical discs, pre-pit signals are reproduced while scanning the track using track servo, so the track pitch is set sufficiently larger than the diameter of the focused light at the focal plane to minimize interference between tracks. It will be arranged in various ways. On the other hand, in the control area of the optical disc of the present invention, since the pre-focus signal is reproduced without adding a track number, it is desirable that the interference between tracks be large. The control tracks of the optical disc of the present invention have a pitch of 0.8 micrometers, whereas in the conventional optical disc, pre-pit rows are formed at a pitch of 1.6 micrometers.

Next, pre-pit signals obtained when the optical discs shown in FIGS. 1 and 2 are reproduced without applying tracking servo will be compared. FIG. 4 is a waveform diagram of a pre-pit signal when the control area of a conventional optical disc is reproduced without applying track servo, and the amplitude of the signal fluctuates greatly. The flat part in the waveform diagram is the signal level from the flat part without guide grooves or pre-pits.If this is Io, the level above the amplitude of the pre-hit signal is t, and the level below is t, then the modulation degree is Indicates (work 1b)/work. In the example of FIG. 4, the value of is fluctuating in the range of α33 to cL05. On the other hand, FIG. 3 is a waveform diagram of a pre-pit signal reproduced from the control area of the optical disc of the present invention without applying track servo, and there is almost no fluctuation in amplitude.
The value of the modulation degree also shows a constant value of 0.28. Unlike conventional optical discs in which the degree of modulation varies greatly, it is not suitable for reading data from the control trunk, whereas the optical disk of the present invention has a constant degree of modulation and is therefore practical.

In the embodiments so far, the pitch of the pre-pit rows in the control area of the present invention is set to half the pitch of other areas.
Although we have described an example fabricated using 1/2, there is nothing special about this value of 1/2. Therefore, in order to find out how much the pitch of the pre-pit row in the control area should be set below to reach a practical level of variation in modulation rate when playing with the track servo removed, we changed the pitch of the pre-pit row in the control area. The modulation depth of each optical disc was measured. The results are shown in Figure 5. The horizontal axis represents the pitch of prepit rows in the control area, which is a percentage of that of other areas, and the vertical axis represents the degree of modulation. Solid line 501
represents the maximum value of the degree of modulation, and the broken line 502 represents the minimum value, and the smaller the distance between the solid line and the broken line, the smaller the variation in the degree of modulation and the better the control area is obtained. Calculating the ratio between the maximum value and the minimum value of the modulation depth from Figure 5 shows that when the pitch of the pre-pit row in the Huntroll area is set to 70% of the pitch in other areas, a value of 3 dB is obtained, and the fluctuation is less than 5 dB. If so, it is considered practical. In other words, it can be said that the pitch of the prepit rows in the control area is desirably 70% or less of the pitch of the prepit rows in other areas.

[Effects of the Invention] As described above, since the prepit row is formed with hits that are less than 70% of the pitch of the prepit row to be reproduced with the track servo applied, the degree of modulation that becomes a problem when reproducing with the track servo removed is reduced. This suppresses the fluctuation to 5 dB or less, making it extremely effective for reproducing control areas and the like. In addition, when producing an optical disk, it is easy to form a prepit array at a pitch of 50% of the pitch of the prepit array to be reproduced by applying a track servo, so the value of 50% mentioned in the example is particularly important. This is a waveform diagram of the pre-pit playback signal that emphasizes this.

FIG. 4 is a waveform diagram of a pre-pit playback signal when the track servo is removed from the conventional optical disk drive area.

FIG. 5 is a correlation diagram between the pitch of a prepit string and the degree of modulation of a prepit signal when this prepit string is reproduced with the track servo removed.

that's all

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a layout diagram of pre-pits in the control area of the optical disc of the present invention. FIG. 2 is a layout diagram of pre-pits in the hunt roll area of a conventional optical disc.

Claims (1)

[Scope of Claims] An optical information recording medium in which information is reproduced by reflected light or transmitted light of the focused light by scanning focused light with a controlled irradiation position, comprising: modulating the intensity of the reflected light or transmitted light; The small holes have small hole rows arranged in the scanning direction of the focused light, and have a region where the small hole rows are arranged at a constant pitch, and the small hole rows have small hole rows arranged in the scanning direction of the focused light. An optical information recording medium characterized by having areas lined up at a pitch of 7/10 or less.