JPH01107322A - Optical disk - Google Patents

Abstract

PURPOSE:To improve the stability of tracking by making the total section length of a bit part where optical depth is except lambda/4 in a control track part longer than that of the part which is not a bit part. CONSTITUTION:The total section length of the bit part 3 in the control track part is made to be longer than that of the part which is not the bit part in the control track part. As the optical depth is zero (that means, flat) at the part except the bit part 3, a tracking error signal (TE) is zero and the TE is detected only at the bit part 3. Therefore, the section where the TE is detected becomes longer than the section of TE = zero. Therefore, due to the influence of decentering, the bit is dislocated from the center of a track. But, the quantity of that dislocation is suppressed to be small. Thus, the bit is not run out from an objective track and a stable tracking characteristic can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical disc used in an optical recording/reproducing device that records and reproduces information by irradiating it with minute laser light.

Prior Art In conventional write-once or rewritable optical discs,
Guide means for guiding the light spot is provided at a predetermined position on the recording medium of the disc. As the guide means, for example, a groove having an optical depth other than λ/4 is used. (
However, λ is the wavelength of a light source such as a laser beam. From now on, λ will be used. ) Also provided is a control track section in which recording and playback conditions are written in advance.

FIG. 2a shows a part of a conventional control track section. 2 is a pit with an optical depth other than λ/4 and represents control information. The total section length of the pit 2 in the control track portion is configured to be smaller than the total section length of the non-pit portion.

Problems to be Solved by the Invention The tracking error signal (TE
) is shown in Figure 2.

Assume that there is a tracking error of ΔX when the beam is at the person' point. Since the optical depth of the control track portion other than pit 2 is O (that is, a flat surface), TE is always 0. In other words, TE is detected only in the pit 2 portion. Therefore, in the conventional control track section, there are more non-pit sections than pit sections, so
There are many parts where TI does not appear, the tracking servo cannot follow, and the beam gradually deviates from the track center due to the influence of eccentricity, resulting in a deviation of ΔX'(>ΔX) at point B'. The greater the eccentricity of the disk, the greater this track deviation, and it is conceivable that the beam may jump out to a track other than the target track while passing through the control track section.

In view of this point, the present invention provides τ of the control track section.
An object of the present invention is to provide an optical disc that has a small influence on X.

Means for Solving the Problems In the optical disc of the present invention, the total length of the pit portions in the control track portion whose optical depth is other than λ/4 is longer than the total length of the non-pit portions in the control track portion. It is an optical disc with a large number of discs.

Function: The optical disc of the present invention has a control track section in which the total section length of pit sections with an optical depth other than λ/4 is made larger than the total section length of non-pit sections in the control track section. , there are more sections where TK is detected than sections where TE is 0, and the influence of the control track section on TK is reduced, so the beam will not jump out to a track other than the target track while passing through the control track section. It disappears.

Embodiment FIG. 1a shows a control track portion of an optical disc according to an embodiment of the present invention. 3 is a pit having an optical depth other than λ/4. As shown in FIG. 1a, the total section length of the pit section in the control track section is greater than the total section length of the non-pit section in the control track section. Figure 1 shows the state of TE when the beam passes on this control track. Assume that there is a tracking error of ΔX at the human point.

In areas other than pit 3, the optical depth is 0 (i.e., a flat surface)
Therefore, TIE becomes O, and τ2 only in pit 3.
is not detected. However, since the total section length of the pit section in the control track section is greater than the total section length of the non-pit section in the control track section, the section where Tic is detected is longer than the section where Tic]E==O. There will be more.

Therefore, although the beam deviates from the track center due to the influence of eccentricity, the amount of deviation can be kept small.

Therefore, the tracking error ΔX' at point B becomes much smaller than in the conventional case, and the beam does not jump out to areas other than the target track, resulting in stable tracking characteristics.

As explained above, the smaller the total section length of the part other than the pit in the control track section, the better T]
The E=O section is reduced, the influence on the TE of the control track section is reduced, and tracking stability is further improved. Therefore, the shorter the length of the portion of the control track section other than the pits, the better; however, if it is too short, it becomes difficult to read the control information. Therefore, it is desirable to set the portions other than the pits as short as possible within a readable range (or, conversely, to set the pit portions as long as possible).

As described in detail of the invention, in the control track section,
The influence of the control track portion on TE can be reduced by making the total length of the pit portions with optical depths other than λ/4 larger than the total length of the non-pit portions of the control track portion. , tracking stability is improved.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a control track section of an embodiment of the optical disc of the present invention, and FIG. 2 is an explanatory diagram of a conventional control track section. 3...Pit with optical depth other than λ/4.

Claims (1)

[Claims] An optical disk having a track guiding means, the control track portion having a signal indicating the type, characteristics, etc. of the disk written by pits having an optical depth other than λ/4, wherein the control track portion has a pit in the control track portion. An optical disc characterized in that a total section length of the portion is greater than a total section length of the portion other than the pit portion.