JPS5938945A - Optical information storing medium - Google Patents

Abstract

PURPOSE:To ensure stable tracking, by forming a tracking guide and signal information pits so as to have their sectional forms which are rectangular to their forming direction. CONSTITUTION:A record layer 3 is formed on a substrate made of a synthetic resin, etc. by means of a thin metallic film of Te, Se, etc. A tracking guide 4 is formed to the layer 3, and signal information pits 5 are formed on the guide 4. The guide 4 has a V-shaped section which is rectangular to its forming direction (direction A in the figure), and the pit 5 has a square section which is rectangular to its forming direction (direction A). Here the level difference, e.g., the depth of the pit 5 is set approximately at (2n+1)/4 (n: a natural number) to a flat surface F.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an optical information storage medium on which information can be written or read using focused laser light.

[Technical background of the invention and its problems]

The information storage medium 2 is a computer disc (CD) used for a digital audio disc (DAD).
) and optical video discs, which are disc-shaped or tape-shaped, and read-only information storage media whose information can be read using focused laser light.
Image files and computer output memory (CO
For recording and playback, it has a disk or tape shape, such as those used in M), and allows information to be transferred to and read from the recording layer using focused laser light. Examples include information storage media and erasable information storage media.

As described above, the track pitch of information storage media has become narrow in order to increase the density of information. For this reason, in order to make the -YC head follow a predetermined track during reading or recording, this type of IW information storage medium is provided with a tracking guide consisting of grooves or convex portions having a step with respect to a flat surface. is formed. Furthermore, if the track number indicating the position where information is recorded, the sector position, and other track position information are recorded in advance, the software for the recording/reproducing device will be easier. It is also equipped with signal information bits consisting of stepped grooves and convex portions (also referred to as a tracking guide with zero reformatting).

The above-mentioned tracking guide and signal information bit are formed by unevenness with respect to a flat surface, and +i'7e is taken as a positive information such as a difference in the amount of light reflected from there. Incidentally, the difference in the amount of reflected light from the unevenness (modulation degree as a signal) is maximum when the level difference between the surface unevenness is λ/4 (λ is '#4', which is the wavelength of the laser used).

same as below. ), and the most stable way to detect track deviation by diffraction or turning of light reflected from the unevenness (this type of detection is also called the push-pull method) is when the level difference between the unevenness is λ/8. It's time. Regarding the width of the irregularities, the conventionally used square cross section (
Formation of signal information bits and tracking guides (sections perpendicular to one direction), the reading laser beam beam 71? Tuto size 1. /38! The maximum modulation degree can be obtained when the width is approximately 0.6 to 0.8 μm, and optimal tracking deviation detection can be performed when the width is approximately 0.6 to 08 μm. For this reason, conventional optical information storage media in which the concavo-convex shape of the cross section perpendicular to the direction in which the signal information bits and tracking guides are formed have a rectangular shape.
/4 depth and a width of 1/34 of the beam spot size of the reading laser beam (for example, a width of about 0.13 to 05 μm for a beam spot size of d08 to 1.6 μrn culmosity). A signal information bit 1 is provided, and a tracking guide 2 having a depth of λ/8 and a width of about 0.6 to 0.8 μm is provided in order to perform optimum tracking deviation detection. It is being

However, if the tracking having a rectangular cross-sectional shape as described above is located in the ID 2, if the focused reading laser beam crosses obliquely to the direction in which the tracking guide 2 is formed, the tracking will be caused by the ID 2. There is a problem in that disturbances are mixed into the focus error detection signal due to diffraction from the errors, ) (wall surfaces of the tracking guide 2, etc.), reducing focus accuracy and tracking stability.

Furthermore, when looking at the light reflection intensity at positions along the track of the optical information storage medium, the characteristics shown in FIG. 2 can be obtained. In the figure, Ll is the light reflection level from the flat surface F (see Figure 1), L is the light reflection level on the tracking guide 2, and L3 is the light reflection level from the signal information bit. υ, L4 is the nine reflections R from the portion of the recording layer where information is recorded.

As is clear from FIG. 2, it has a rectangular cross-sectional shape,
As described above, in the case of having the width, the difference between the light reflection level L2 on the tracking guide and the light reflection level L3 from the signal information bit is not so large. For this reason, there is a problem in that the S/N ratio when reading signals from the signal miscellaneous pits becomes poor. Still, for the same reason, there is a problem that the start position P1 or the end position P2 of the tracking guide 2 may be mistakenly detected as part of the signal information bits. For such problems,
By narrowing the width of the tracking guide without changing its cross-sectional shape and depth, the level of light reflection on the tracking guide can be increased. However, if the width is changed, the tracking deviation detection signal obtained by diffraction or turning of the light reflected from the tracking guide becomes small, making stable tracking impossible.

[Purpose of the invention]

The present invention has been made based on the above circumstances.By increasing the level of light reflection on the tracking guide, it is possible to accurately read signals from signal information bits, and to reduce the amount of light reflected from the tracking guide. Shidano'
An object of the present invention is to provide an optical information storage medium capable of performing stable tracking by increasing the track deviation detection signal obtained by turning C times Jfr-'.
The target is

[Summary of the invention]

The present invention solves the problem of diffraction of light reflected from a tracking guide.
The cross-sectional shape of the signal information bit and the tracking guide has been designed so that it is possible to detect a large l/rack deviation by turning, and to obtain a large degree of modulation for the amount of reflected light from the signal information bit. They are characterized by being formed with different .

[Embodiments of the invention]

Next, the optical information storage medium of the present invention will be explained with reference to the drawings.

FIG. 3 is a schematic perspective view M showing an embodiment of the present invention. In the figure, reference numeral 3 denotes a distribution IA provided on a not-illustrated substrate made of synthetic resin or the like.

As the recording layer 3, a metal thin film such as Te or Sc is generally used, and satisfies conditions such as a low melting point, a low boiling point, and a low thermal conductivity. A tracking guide 1'4 is formed on the recording layer 3 at t7, and a pit 5 for Shingetsu information is further formed on this tracking guide 4. The front station tracking guide 4 has a V-shaped cross section perpendicular to its formation direction (direction toward the third arrow in the figure). Further, the signal information bit has a rectangular cross-sectional shape perpendicular to its formation direction (in the direction of the third arrow in the figure).

Here, the step dimension of the signal information bit 5 with respect to the flat surface F (see Part 3), for example, the depth, is a value close to (2n+14) (however, n is 0 or a natural number, and λ is h
fe, n'l (the wavelength of light).

This is because in order to make the light reflection level from the Shingetsu information bit 5 sufficiently lower than the light reflection level from the flat surface F to accurately perform erasure reading from the signal information bit 5, This is because the phases of the lights reflected from both need to be shifted by about λ/2.

In addition, the width of the signal information bit 50 is, for example, approximately 1/3 of the beam spot size of the reading laser beam, so that relatively Inuhikoyori ζ modulation dust (meaning that the light reflection intensity is low) is rubbed. Like Fu: ′).

In addition, since the tracking guide 4 has a V-shaped cross section perpendicular to its formation direction as shown in +'+iJ l, the influence of light reflected by the inclined surface 4a of the tracking guide 4 is large, and the reading is difficult. The reflected light of the first refractive index is easily bent to a large extent, and the track deviation detection signal due to the diffraction gloss turn can be made thicker than that of the conventional rectangular cross section. Moreover, the phase of the light that should be reflected by the inclined surface 4a of the tracking guide and interfere with each other varies depending on the position of the reflecting inclined surface 4a, so that a higher light reflection intensity can be obtained compared to the conventional one with a square cross section. Something will happen. However, the depth and width dimensions of the tracking guide 4 are not necessarily limited to the conventional dimensions explained in the technical background of the invention, but may be any convenient value in relation to the formation process of the signal 111 information bit 5. It is also possible to do so. Although not shown, a protective layer is provided on the surface of the recording layer 3 to protect it.

As is clear from the above description, the optical information storage medium configured in this manner can perform stable tracking using the V-shaped cross-sectional tracking guide, and also has a low light reflection level from the tracking guide. It is possible to ensure a large difference in the light reflection level between the light reflection level from the signal information bit, and the signal can be read accurately from the signal information bit, and the above two effects are also ensured. At the same time, it becomes possible to facilitate the formation process of the tracking guide and the signal information bit.

Note that the above-mentioned embodiment is merely an example, and various modifications can be made within the scope of the gist of the present invention.

For example, the cross-sectional shape of a tracking guide is often not limited to a V-shape, but as shown in Figure 4 (, ), the cross-sectional shape at right angles to the direction in which the tracking guide is formed is U-shaped, which approximates a V-shape. Alternatively, as shown in FIG. 4(b), the cross-sectional shape perpendicular to the direction in which the tracking guide is formed may be a trapezoid, or a cross-sectional shape similar to these may be used. Even if it is shaped like this, the above fruit; 71
f! Due to the influence of the 1/1 slanted surface, it is possible to achieve stable racking and a light reflection intensity of 1°.

Also, regarding signal information bits, implementation 1. It is limited to the rectangular cross section described in '11, and is not limited to the CJ, but as shown in Figure 5 (a), the signal information 41: perpendicular to the direction in which the J pit is formed; the shape of the new surface is U-shaped. Figure 5 (h)
As shown in K, the cross section perpendicular to the direction in which the signal information bits are formed may have a trapezoidal shape or a cross-sectional shape similar to this. In short, the cross-sectional shape may be different from the cross-sectional shape of the tracking guide so that a high degree of modulation can be obtained.

In addition, in the above explanation, the case where the iU information bit and the tracking guide are formed in four parts is explained, but even if these parts have the same cross-sectional shape and are formed with convex parts, the characteristics of reflected light will change. Even if formed in this way, exactly the same effect can be achieved.In the embodiment shown in FIG. 3, the tracking guide 4 and the signal information bit 5 are formed without being separated. Although the above description has been given, it is also possible to form these separately as shown in FIG.

〔Effect of the invention〕

As is clear from the above description, the optical information storage medium of the present invention is capable of accurately reading signals from signal information bits by increasing the light reflection level on the tracking guide. In addition, it has excellent effects such as increasing the track deviation detection signal obtained from the diffraction pattern of the light reflected from the racking guide and enabling stable tracking from time to time.

[Brief explanation of the drawing]

iIB Figure 1 is a schematic diagram showing a conventional optical information storage medium, Figure 2 is an explanatory diagram of the intensity of light reflection at IN along the track of the conventional optical information storage medium, and Figure 3 (
Figures 4(-) and 4(b) show a tracking guide in another embodiment of the optical information storage medium of the present invention. Schematic sectional views No. 5(a) and 5(b) are schematic sectional views showing signal bits in another example of the optical information storage medium of the present invention. 3... Recording layer, 4... Tracking guide, 5...
・Signal information bit, F...Flat surface.

Claims (8)

[Claims] (1) Equipped with a tracking guide for detecting track deviation using the Bushzol method and a signal information bit that stores track position information, it is possible to at least read the information using a focused laser beam. An optical information storage medium characterized in that the tracking guide and the signal information bit are formed to have different cross-sectional shapes perpendicular to the direction in which they are formed. (2) The optical information storage medium according to claim 1, wherein the tracking guide has a substantially V-shaped cross-sectional shape with an angle in the direction in which the tracking guide is formed. (3) The optical information storage medium according to claim 1, wherein the tracking guide has a cross-sectional shape perpendicular to its formation direction that is substantially U-shaped, approximately approximating a V-shape. (4) The optical data storage medium according to claim 1, wherein the tracking guide d5 has a trapezoidal cross-sectional shape perpendicular to the direction in which it is formed. (5) The optical information bit according to claim 1, wherein the cross-sectional shape perpendicular to its forming direction is U-shaped. Storage medium/ (6) The signal information bit has a substantially rectangular cross-sectional shape perpendicular to its formation direction. Media/ (7) The signal information pit has a substantially trapezoidal cross-sectional shape perpendicular to its formation direction! The optical q' type information storage medium according to claim 1, which has one key feature. (8) The signal information pit has a height difference with respect to a flat surface of approximately (2n-1-1)/4 (where λ is the wavelength of the reading radar light and n is O or a natural number). An optical information storage medium according to claim 1, characterized in that: