JPS6228944A - Optical information recording and reproducing disk - Google Patents

Abstract

PURPOSE:To increase the playback amplitude of a pit by increasing the width of a groove track for recording and reproducing information, decreasing the pit width of a signal formed as a pit, and making the depth of the groove and pit less than one-eighth as large as wavelength. CONSTITUTION:The width W1 of the track of a groove 1 and the width W2 of the pit 2 of a projection/recess pitch signal are so set that W1>W2. Then, the step between the groove 1 and pit 2 is set deeper than optical path length lambda/8, where lambda is wavelength. Then, information is recorded in a thin film layer at the groove part and its dot signal is reproduced. In this case, when the spot diameter of laser light is denoted as S0, the amplitude decreases in a direction of larger than S0 and is maximum in an area where the pit width W2 is S0/2.

Description

[Detailed description of the invention] Industrial applications The present invention is capable of recording, reproducing, and erasing large amounts of data.

The present invention relates to an optical information recording/reproducing disk used in the field of optical disks that enables high-speed access.

15. Conventional technology It is necessary to track laser beams with high precision on optical discs, and for this purpose, a groove with a step with an optical path length of λ/8 is formed on the substrate for recording/reproducing or erasable optical discs. A method has already been used in which tracking is controlled by detecting changes in the intensity distribution of far-field diffracted light of reflected light from the step.

Furthermore, a method is used in which a track address or a sector signal is previously formed on the substrate as a concavo-convex pit signal, and includes a reproduction-only signal, and information is recorded and reproduced in the empty groove portion.

Problems to be Solved by the Invention Signals recorded and reproduced on groove tracks having a step with an optical path length of λ/8 vary depending on the depth d of the step and the width W1 of the track.

Also, the reproduction signal from the reproduction-only concavo-convex pit changes depending on the level difference d of the pit and the width W2 of the pit.

The above two types of signals have opposite depths, till
It has an optimal condition at π.

Furthermore, the dragging amplitude for trunking control also varies depending on the depth d and the width W1 of the groove.

A groove track that optimizes these three types of signals.

It is necessary to provide the uneven pits on the same substrate.

Means for Solving the Problems The present invention provides a disc comprising a thin film layer capable of optically recording and reproducing information, a guide groove trunk for laser light consisting of unevenness, and a sector signal consisting of uneven pits. The track width W of the groove and the pit width W2 of the pit signal are selected so that W2<Wl, and the depth of the groove track J and the pit are the same and are selected to be shallower than the optical path length of λ/8. This is an optical information recording/reproducing disc.

Effect: When configured as above, the reproduction width of the recorded signal and the reproduction amplitude of the pit signal increase, and the amplitude of trussogging becomes stable against fluctuating groove width.

Actual Mli Example In the present invention, first of all, the width W1 of the groove track and the width w2 of the uneven pit signal are formed so that Wl>W2 as shown in FIG. do,.

Next, the steps of the grooves and pits are selected to have an optical path length of λ/8.

Information is recorded in the thin film layer in the groove, and the dot signal is reproduced.

As shown in Fig. 2, the reproduction amplitude of the pit signal decreases in the direction in which the pit width becomes smaller, and if the spot diameter of the laser beam is S, then the amplitude decreases in the direction larger than so. .

The maximum width W2 is -1, which is Hs. This is an area where However, the depth of the step in focus is 1, when the depth is λ/4n where n is the refractive index of the substrate, and it decreases as it becomes shallower, so the pit width W2 is 1, I choose W2-TSo.

Next, as shown in Fig. 3, the recorded re-gyushinkyu amplitude in the groove is large in the direction where there is no groove, the groove width w, = -〇, and in the region where the groove width becomes infinite. The amplitude can be obtained.

However, in order to obtain the j-ranking amplitude, the groove width is important. FIG. 4 shows the trunking amplitude and groove width.

When the groove width W1 is small, the dragging amplitude is small, and w
>s, it is almost saturated.

From FIGS. 3 and 4, it is clear that the wider the width W1 of the groove trunk, the better, and the recording image width will increase. As W, choose d:, W1~SoK.

Next, there are independently different optimal conditions for the depth of the groove track and the depth of the O/pit signal.
Providing two or more depths on the same substrate requires complicated methods for preparing the master, and as shown in Figures 2 and 3,
The depths of the grooves and pits are selected to be shallower than λ/8n. At this time, as shown in FIG. 3, a large value is obtained as the recorded amplitude of Machioshin-Yumi.

As shown in Figure 4, the width of the groove track is the spot diameter S. By making it larger, the tracking amplitude approaches saturation, and a stable amplitude can be obtained against fluctuating groove widths. For the preparation of the master, a glass disk with 7 optical resists is used. The groove portion is irradiated with a power twice or more that of the pit signal portion, and this is developed.

Pit width w2 is 0.3 μm, groove width w1 is 0
, 87zm. Laser wavelength d for recording and reproduction:
, 830 nm, a laser spot is formed using a lens with an aperture of 1-1 and an NA-0.5. Spot diameter s0 is approximately 0.9
It becomes μm.

A stamper is formed from this master disk, and grooves and pits are transferred to polycarbonate resin by injection molding using this stamper.

The refractive index of polycarbonate resin is 1, n=1.58. In this substrate, a step with an optical path length λ/8 has a depth λ
It can also be stopped by /s n, which is 660 nm. By choosing the resist thickness, the depth on the substrate can be reduced to λ/8 n
Make it shallower. It becomes approximately 600 nm. ]: Choose sea urchin.

On this substrate, Te0x(0(x(2,0)(Te and T
A thin film of 1" is formed with a mixture of e O2 as the main component.

The recording/reproduction signal amplitude has a groove width of -ZS. From S. By making the grooves shallower, it is improved by about 10%, and by making the grooves shallower, it is improved by about 10%.

Mixed, V/1-, S. , d=λ/sn, the C/N ratio of the recorded/reproduced signal was improved by about 2 dB.

Also, because of the wide groove, the dragging amplitude is stable with respect to the groove width, and for a groove of Wl''', 80.d-λ/811,
At Wl = So, d = 600 nm, we were able to obtain the same tracking amplitude and at the same time achieve stable amplitude with respect to fluctuating groove width.

Effects of the Invention As described above, according to the present invention, the width of the groove track for recording and reproducing information is increased, the pit width of the signal formed in advance as a pit is decreased, and the depth of the groove, J, and pit is increased. By making the optical path length shallower than λ/8, the reproduction amplitude of the recorded signal can be increased. Moreover, the reproduction amplitude of the pit signal can also be increased. Further, it is possible to obtain effects such as the tracking amplitude being stabilized against fluctuations in groove width.

[Brief explanation of drawings]

FIG. 1 is a plan view of a main part of an optical information recording/reproducing disk according to an embodiment of the present invention, FIGS. 2 and 3. FIG. 4 is a characteristic diagram for explaining the disc. 1...groove, 2...pit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Pit country middle (uf2!U Figure 3/2' So So /2'S. Groove middle (OJt) Figure 4 Groove 1VJ width (obstructed)

Claims (2)

[Claims] (1) In a disk consisting of a thin film layer capable of optically recording and reproducing information, and a substrate containing a laser beam guide groove track consisting of unevenness and a sector signal consisting of uneven pits,
Track width W_1 of guide groove and pit width W of pit signal
_2 is selected so that W_2<W_1, the depths of the groove track and the pit are the same, and are selected to be shallower than the optical path length of λ/8. (2) The track width W_1 is selected so that W_1>s_0 with respect to the spot diameter s_0 of the laser beam used for reproduction, and the pit width W_2 of the pit signal is set to W_2.
The optical information recording/reproducing disc according to claim 1, wherein the optical information recording/reproducing disc is selected so that ≒1/2s_0.