JPS60121553A - Optical recording disk - Google Patents

Abstract

PURPOSE:To obtain an optical recording disk which has little external disturbance to a tracking error signal and can count the number of sectional grooves precisely at the time of retrieval by connecting bits in a format area with each other by fine grooves. CONSTITUTION:A space between a bit a1 and a bit a2 in a format area of an optical recording disk is connected by a groove b1 having width thinner than those of the bits a1 and the a2. A space between the bit a2 and a groove 2 is connected with a fine groove b2. With the constitution, when light beams travel along a guide track, diffraction is generated by the groove b1 between the bits a1 and a2, a tracking error signal is produced, and a large external disturbance will not occur. When the light beams travel between the bits a1 and a2 in an arrow X direction, and pass through between them at the time of retrieval, diffraction is generated by the groove b1, and a signal crossing the groove is produced, thereby making accurate retrieval possible. A width W1 of the bit part and a width W3 of the groove have almost the same value, and a width w2 of the connecting groove is preferably >=1/2 of the width w1 and w3.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a light beam used in a device that focuses light from a laser or the like into a microscopic light spot to record and reproduce signals at high density on a rotating disc-shaped optical recording medium. It relates to a recording disk, which can record and reproduce signals at a significantly higher density than conventional magnetic disks, etc., and realizes a large-capacity memory. In particular, the present invention relates to formatting of optical recording discs.

Structure of a conventional example and its problems FIG. 1 shows an outline of a formatted grooved optical recording disk, and FIG. 2 shows an enlarged cross-sectional view of the grooved optical recording disk.

FIG. 1 shows a plan view of an optical recording disk. A known optical guide track is pre-provided on the disc.

A groove of uniform depth is used as one of the guide tracks, and signals are recorded and reproduced along this groove, that is, while tracking an arbitrary groove. FIG. 2 shows an enlarged cross-sectional view of this grooved optical disk. A groove 2 having a width W, a depth d, and a rack pitch p is provided in a transparent disk base material 1, and an optical recording material layer 3 is formed thereon by vapor deposition or the like.
Furthermore, a protective layer 4 is formed thereon. The recording/reproducing light 6 records/reproduces a signal along any specified groove using a known tracking technique.

The depth of the groove suitable for tracking is λ/8 (λ is the wavelength of the light source).0 The groove 2 shown in Figures 1 and 2 extends in a spiral pattern over the entire signal recording/reproducing area on the disk. In FIG. 1, only one groove 2 is shown to simplify the drawing. In FIG. 1, A1. A2...An indicates a format t4tr area in which, for example, a groove-specific address signal and a sector number within this address groove are recorded in advance for formatting the recording area on the disk. On the other hand, area B1. B2...Bn is the format area shown in Figure 1 that indicates an information area for recording and reproducing signals, and address signals and sector signals are generally formed by intermittent grooves shown in Figure 2. . In other words, in many cases, a signal is generated at the same time as the groove 2 is formed on the disk as a concave and convex bit, and this method is also useful for disk duplication technology, since a large number of formatted disks are formatted at high speed. There are effects that can be created.

FIG. 3 shows a specific example of a format signal using the conventional uneven bit. FIG. 3 shows a partially enlarged view of one groove in the circumferential direction of the disk.

In the figure, F indicates one plane, and H indicates a pinot of depth d) (a
l + a2) and groove 2 are shown. Area A is a format area, as shown in FIG. 1 A1. A2... indicates one of the areas of An, and B is the information area B1. B2... mark, Bn 1
Show one. a 1 and a 2 indicate focus points constituting address signals and sector signals. This pinot) a 1,
If the depth of a2 is made the same as the depth of groove 2, it has the advantage of making it easier to create the face of the optical disc, but it is not necessarily necessary to make the depth the same.

The conventional formatted groove shown in FIG. 3 allows light to pass through an area between bits a1 and B2 when detecting a tracking signal using a differential method to detect changes in the far-field pattern of reflected light from a well-known disk. When passing through, the tracking error signal becomes zero and no output is generated, so
When the light beam passes through the format areas A1 . . . An in FIG. 1, it becomes a factor that causes disturbance in the tracking error signal. Particularly, when the servo loop of the tracking control system is OFF, a particularly large disturbance signal is generated in the tracking error signal.

Furthermore, in the conventional formatted groove shown in FIG. 3, when accessing any location on the optical disk at high speed, the minute light beam is directed in the radial direction of the disk, for example as indicated by the arrows X or Y in FIG. Move fast across the ditch in the direction.

For example, when the light crosses the groove at the Y position, a signal can be generated to detect that the light has crossed the groove, similar to the detection of a conventional tracking error signal. Therefore, the number of grooves crossed by the light beam can be counted, the distance traveled by the optical dome (optical head) can be measured, and the search can be controlled.

However, in Fig. 3, the light beam beeps) al, 82
When passing through the area indicated by arrow This results in a decrease in

OBJECTS OF THE INVENTION The present invention improves the format area of the above-mentioned conventional optical recording disk, and reduces disturbance to the tracking error signal.
Further, it is an object of the present invention to provide an optical recording disk having a formant area that allows accurate counting of the number of transverse grooves during retrieval. This is an optical recording disk having a format signal of 0 bits a1 and B2 show an example of
a1. Leave a groove B11 narrower than the width of a2. Similarly, the bit a2 and the groove 20 are also connected by a narrow groove b2. In this way, all the bits of the format area are connected to each other by narrow grooves. Generally, such grooves are created by coating a glass master with a photoresist with a thickness corresponding to the groove depth d and exposing it to light using a laser cutting machine.

This is done by performing casoteng. Therefore, during force sowing, the pit shown in FIG. 3, al.

a 2 , enough laser power is applied to the groove 2 part to completely remove the 7 photoresist during the development process,
Weak laser power is applied to the connecting portions bl and b2, and even after the development step, a shallow and narrow connecting groove that does not reach the original glass can be obtained.

As mentioned above, by providing the thin connection grooves between the format pits, when the light beam travels along the track inside the dormitory, diffraction occurs due to the thin grooves b1 even between the pits "1 r" 2, resulting in a tracking error signal. , and the large disturbance as explained in FIG. 3 no longer occurs. Furthermore, when searching in FIG. 4, when the light beam travels between pits a1 and a2 in the direction of arrow Since it generates a signal that crosses the area, accurate search becomes possible.

FIG. 6 shows a plan view of the guide track of FIG. 4. W
l indicates the width of the pit portion, W2 indicates the width of the connecting groove, and W3 indicates the width of the groove portion, widths W1 and W3 have approximately the same value, and the widths of Wl and W3 are 0.5 μm to 0.6 μm. When, W2 is less than % of the width of wl and w3, preferably 0.10 to 0.2
A width of μm is appropriate.

Effects of the Invention Since the optical recording disk of the present invention is configured as described above, there is little disturbance to the tracking error signal, and the number of transverse grooves can be accurately counted during a search.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an example of an optical recording disk, FIG. 2 is an enlarged partial sectional view of the optical recording disk, and FIG. 3 is a perspective view showing an example of how to input a format signal in a conventional optical recording disk. FIG. 4 is a perspective view showing how to input a format signal according to the present invention, and FIG. 5 is a plan view of FIG. 4. a1. a2... pit, bl, b2...
...A narrow groove.

Claims (1)

[Scope of Claims] (1) A format signal consisting of a plurality of continuous uneven pits is provided in the format area, and between the pits,
An optical recording disk characterized in that the pits are connected by narrow grooves that are less than % of the width of the pits. 7)) The optical recording disk according to claim 1, wherein the depth of the groove connecting the pits is shallower than the depth of the pits. (3) The optical recording disk according to claim 1, wherein the pit depth in the format area and the groove depth in the information area are the same.