JP2924877B2 - How to play information - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for reproducing information recorded on an optical information recording medium.

[0002]

2. Description of the Related Art An optical information recording medium (hereinafter referred to as an optical disk) is a replaceable storage medium having a capacity several tens of times that of a magnetic disk. On the optical disc by unevenness, or
Small holes (hereinafter referred to as pre-pits) that modulate the reflected light or transmitted light of the irradiated light due to the difference in reflectance, and guide grooves for scanning the Tohto light along the track are formed. The optical information recording device uses a focus servo that focuses the convergent light on the recording surface of the optical disk, and a track servo that controls the position of the focused light so that the center of the focused light does not deviate from the guide grooves, between the guide grooves, or from the pre-pit row. The focused light can be scanned on the pre-pit row.

[0003]

The manufacturer often records address and control information in advance in the form of pre-pits. The address is reproduced by applying the track servo, and the control information is reproduced by applying the track servo, and is reproduced without applying the track servo. If the control information to be reproduced without applying the track servo is recorded in a common format, it is possible to obtain the control information on the optical disks having different tracking systems, sector formats, etc. before applying the track servo. An area in which control information to be reproduced without track servo is recorded (hereinafter, referred to as a control area) is not provided with a guide groove because the track servo is not applied, and a pre-pit row in which pre-pits are arranged in the scanning direction of the focused light. Consists of only This pre-pit row is recorded with the same modulation over several tens to several hundred tracks, and often forms a control area similar to a bar code. When the pre-pits are made of irregularities on the reflective surface, the intensity of the reflected light decreases when the focus of the Shuto light is on the pre-pit, and when the focus is outside the pre-pit and irradiates a flat surface, the reflected light Strength increases. Information can be reproduced by a pre-pit signal utilizing the modulation of the reflected light. However, when this pre-pit signal is reproduced without performing track servo, a problem has not necessarily been achieved. When the control area is reproduced, the track servo is not applied, so that the focused light does not always irradiate the pre-pit row but may irradiate between the pre-pit rows. Since the plane between the pre-pit rows is a flat surface, while the focused light scans there, the state where the amount of reflected light is large continues, so that the degree of modulation of the amount of reflected light is significantly reduced. On the other hand, when the focused light scans the pre-pit row, the degree of modulation increases. Therefore, there is a problem that the modulation degree of the pre-pit signal varies greatly and it is extremely difficult to obtain control information therefrom.

Accordingly, the present invention is intended to solve such a problem. It is an object of the present invention to reduce the fluctuation of the degree of modulation even when reproducing a pre-pit signal without applying a track servo, thereby making it easy to reproduce information. It is an object of the present invention to provide a method for reproducing information from an optical information recording medium.

[0005]

According to the present invention, there is provided an information reproducing method comprising the steps of: forming an optical information having at least two pre-pit rows in which adjacent tracks at a predetermined track pitch and a plurality of pre-pits are formed in a row; A method for reproducing information recorded on a recording medium by irradiating focused light and scanning the reflected light or transmitted light of the focused light, wherein at least two of the pre-pit rows in the optical information recording medium are , Adjacent to each other at a first pitch in parallel with the direction of the pre-pit rows, and the first pitch is an area that is equal to or less than 7/10 of a track pitch in the track. The apparatus is characterized in that focused light is scanned without applying track servo, and information recorded in the area is reproduced.

Further, in the above method, the area of the pre-pit row in the optical information recording medium can be used as a control area.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments. FIG. 1 shows an arrangement of prepits in a control area of an optical disk (optical information recording medium) used in the method of the present invention. On the other hand, FIG. 2 shows an arrangement diagram of prepits in a control area of a conventional optical disk. Compared to the method of arranging the pre-pits 201 in the control area of the conventional optical disc, the pre-pits 1 in the control area of the optical disc used in the present invention are different.
The arrangement of 01 is dense in the direction perpendicular to the scanning direction of the focused light. In the conventional optical disk, the track servo is applied to reproduce the pre-pit signal while scanning on the track.
Since the track pitch is set to be sufficiently larger than the diameter of the focused light at the focal plane so as to reduce the inter-track interference, the arrangement is as shown in FIG. On the other hand, in the optical disk used in the present invention, since the control area adopts a reproducing method of reproducing the pre-pit signal without applying the track servo, it is preferable that the inter-track interference is large. Therefore, the pre-pit as shown in FIG. In this embodiment, the control tracks of the optical disk used in the present invention have a pitch of 0.8 μm.
Each pre-pit row is formed at a pitch of 6 micrometers.

Next, the pre-pit signals obtained when the optical disk shown in FIGS. 1 and 2 is reproduced without applying tracking servo will be compared. FIG. 4 is a waveform diagram of a pre-pit signal when a control area of a conventional optical disk is reproduced without applying track servo, and the amplitude of the signal fluctuates greatly. Flat portion guide groove in the waveform diagram, this signal level from the flat portion having no prepits as I _0, when the level above the amplitude of the prepit signal and I _t, the lower level and I _b, the modulation indicating the degree (I _t -I _b) /
The value of I ₀ fluctuates in the range of 0.33 to 0.03 in the example of FIG. On the other hand, FIG. 3 is a waveform diagram of a pre-pit signal reproduced from the control area of the optical disk according to the present invention without applying track servo. Is shown. If the modulation degree fluctuates greatly as in the conventional optical disk, it is not suitable for reading out the data of the control track, whereas in the method of the present invention, the optical disk has a constant modulation degree and can be said to be practical. .

In the above-described embodiments, an example has been described in which an optical disk prepared by setting the pitch of the prepit row in the control area of the present invention to one-half the pitch of the other areas is used. There is no special value.
Therefore, in order to clarify whether the pitch of the pre-pit row in the control area should be less than or equal to the practical level, the fluctuation of the modulation rate when reproducing without track servo is changed, the pitch of the pre-pit row in the control area is changed. The optical disks were manufactured and the degree of modulation was measured.
The result is shown in FIG. The horizontal axis indicates the percentage of the pitch of the pre-pit row in the control area in other areas, and the vertical axis indicates the degree of modulation. A solid line 501 indicates the maximum value of the modulation factor, and a dashed line 502 indicates the minimum value. The smaller the distance between the solid line and the broken line, the smaller the fluctuation of the modulation factor and a better control area is obtained. When the ratio between the maximum value and the minimum value of the modulation degree is calculated from FIG. 5, when the pitch of the prepit row in the control area is 70% of the pitch of the other areas, 3d
A value of B is obtained, and if the fluctuation is 3 dB or less, it is determined to be practical. In other words, it can be said that it is desirable that the pitch of the pre-pit row in the control area be 70% or less of the pitch of the pre-pit row in other areas.

[0010]

As described above, since the pre-pit row is formed at a pitch of 70% or less of the pitch of the pre-pit row to be reproduced by applying the track servo, the modulation degree which becomes a problem when the reproduction is performed without the track servo is performed. Is suppressed to 3 dB or less, which is extremely effective for reproducing a control area or the like. In manufacturing an optical disk, it is easy to form a pre-pit row at a pitch of 50% of the pitch of a pre-pit row to be reproduced by applying a track servo. Therefore, the value of 50% mentioned in the embodiment is particularly important. Emphasize that.

[Brief description of the drawings]

FIG. 1 is a layout diagram of prepits in a control area of an optical disc used in the method of the present invention.

FIG. 2 is a layout diagram of prepits in a control area of a conventional optical disc.

FIG. 3 is a waveform diagram of a pre-pit reproduction signal when a control area of the optical disc of the present invention is reproduced without a track servo.

FIG. 4 is a waveform diagram of a pre-pit reproduction signal when a control area of a conventional optical disc is reproduced without a track servo.

FIG. 5 is a correlation diagram between a pitch of a prepit row and a modulation degree of a prepit signal when the prepit row is reproduced without a track servo.

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Claims (2)

(57) [Claims] 1. A method of irradiating converged light with information recorded on an optical information recording medium having at least two prepit rows in which adjacent tracks and a plurality of prepits are formed in a row at a predetermined track pitch. A method of reproducing information by scanning and reproducing the reflected light or transmitted light of the focused light, wherein at least two of the pre-pit rows in the optical information recording medium are parallel to a direction of the pre-pit rows. The first pitch is one of the track pitches in the track.
A method for reproducing information, wherein the area is not more than 7/0, and focused light is scanned without applying track servo to the area to reproduce information recorded in the area. 2. The information reproducing method according to claim 1, wherein the area of the pre-pit row in the optical information recording medium is a control area.