JPS59207433A - Recording and reproducing system with high density - Google Patents

Abstract

PURPOSE:To attain the recording with high density by recording bit trains of >=2 series in parallel to each other and in a synchronous state within a globe set on a magnetic disk and detecting a diffraction pattern of the return light which tracking the bit trains with light spots. CONSTITUTION:Pits H1 and H2 of two series forming a paired tracks are recorded to a light spot S. The light delivered from a laser light source 10 forms the spot S on the pits H1 and H2 through a polarized beam splitter PBS11, a collimator lens 12, a lambda/4 plate 1 and an objective lens 14. The return light of the spot S travels back and is reflected by the PB11 to be made incident to a 2-split photodetector 15. Then the information recorded on the paired tracks is reproduced through detection levels A' and B'. Thus the recording is possible with high density.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high-density recording and reproducing method for recording and reproducing information on an optical disc.

[Background technology and its problems]

The method of recording and reproducing information using an optical disk currently has the highest recording surface area 'f'. This recording surface severity σ is determined by the track pitch P, the transmission efficiency η,
When the wavelength is input and the lens is opened, ``】If the melon is NAη 2NA, it is approximately expressed as σ=-・□.

P input From the above equation, in order to increase the recording surface distribution σ, it is necessary to reduce NA □, which is related to the optical system, that is, to reduce the diameter of the spots that are mutually irradiated with light, and to reduce the track pinch P. However, due to the effects of skew, cross-storage, etc., there is no choice but to develop a new TEPAIS and improve the accuracy of the two-machine system, and consumer products are limited by price.

Therefore, a multi-level recording/reproducing power formula has been proposed to increase the transmission efficiency η.

This is the depth of the pit or the four values (0, 0,
i, 2, 3) and then reproduces this.

However, even in the case of this method, there are some problems with the recording and reproduction characteristics of the optical disk, and the recording surface F' Kσ
Although it is twice as large, it is still insufficient for high-density recording and reproduction such as technical video signals.

[Invention 1] This invention utilizes the spot diameter already realized in current recording devices to form a focus so that the recording surface density is at least double, and has already been put into practical use. 11
) High sparrow record that can be played on live equipment (11th live method) (j
17.

[Outline of the invention]

In order to achieve the objects stated in item 2, this invention records two or more series of pit chests, each having independent information, in parallel in a rotated state on a spiral globe formed on an optical disk. , the said glove] 1. There is a high-density recording and reproducing method that allows the above-mentioned independent information to be read from the diffraction pattern of the returned light detected while tracking with a spot. It is even better to raise the second level.

[゛) Absolutely defeated]

Currently, the pitch recorded on optical discs is determined by considering the influence of the semiconductor laser's wave R, crosstalk, and skew.
The track width is approximately 1.6 lm, and it is designed to be read with a spot diameter of 0.8p7m. However, on the recording side, when using a gas laser light source using Al-J7, etc., and setting the NA to about 0.9, the recording speed is about 0.4 gm1.
73 sports.

It is easy to record a pit with a diameter of 1.

Therefore, in the high-density recording and reproducing method of the present invention, such information pits are formed so as to be recorded in parallel in two series of pits (hereinafter referred to as paired tracks) on one track, and these are recorded as one 1q raw spot on the reproducing side.・It is designed to be read out once.

As the principle of 1 readout, the principle of the push-pull method, which is already in practical use at present, is used.

In the push-pull method, as shown in the 11th Δ, the optical disc D
The return light reflected from
The bright U1) pattern of each photocathode of the divided photodetector 111r, which is detected by the divided photodetector PD and used to detect the focus error signal, can be as shown in FIG. Are known.

That is, when the pit H of the track is away from the center of the spot s, the brightness and darkness of the photocathode pattern becomes asymmetrical on the left and right sides as shown in 1.2, 3, 7, and 8.9 of the 2nd IA. The two detection signals generated by the divided photodetector FD are different from each other.

Therefore, as shown in FIG. 3, pit H1 forms a pair track for one spora l=S.

When the configuration is such that a laser beam is irradiated to H2, and the return light from this pair is input to the two-split photodetector FD, when there is only pit H1, as shown in FIG.
When there are Hr and H2, g 3 +g+(b) is detected, and when there is only H2, a pattern is detected after light 1 as shown in FIG. 3(C).

Therefore, the detection signal of the photocathode divided into two is A.
'', B', there is mutual interference, but there is at least one spora).If specular reflection is included, four types of detection signals are obtained.

Figure 4 shows the pair track focus H,, H2 and I+), and the recorded information is the trunk width P(1,
6pm) is formed at intervals of approximately 0.1 to 0.2 gm, and this is read by one Subo-nt S on the playback side. Do it like this.

The optical system on the reproduction side includes a laser light source 10, an oblique beam beam splitter, a collimation lens 12. I/
4 A plate 13. Objective lens 14 and two-split light detection device 1
5, etc., and the two-split photodetector: t'l
At step 15, the brightness and darkness intensity of the pattern included in the return light from the optical disc is detected.

Although not shown, the tracking servo may be performed using a known three-spot method, and the focus servo may be performed using the -Jl one-point focusing method.

The table shown in FIG. 5 shows the signals detected by the two-split photodetector 15 through simulation.

This chart shows pit depths of /8. Bint separation: O,l, 0.2 p-m, pit width: 0.4
This figure shows the intensity distribution of two types of patterns obtained when the intensity is 1 Lm and 0.5 pm, and the case where there are no pits at all, that is, the case of a mirror surface part, is taken as 100%.

From this IRI table, if you form a pair track with a pit width of 0.4 gm and a separation of 0.1 gm, and look at the intensity of the reflected light, in the case of ■, that is, if there is only a pit l-H, the mirror surface 68.5% of the reflection intensity of
Therefore, it can be seen that the foul strength for the side without pits is 89.5% by 71.

However, in the case of ■, that is, when the focus H,,H2 exists on both paired tracks, both are 699% (70%
) is the foul strength.

Also, in this state, the focus separation is Mira 0.2)L
If you expand it to m, in the case of ■, that is, there is only pit H1.
J, 1 go is the same at 685%, but the force out of focus is 9
1.2% = slightly larger lending rate.

And, in the case of ■ with pit H1 + H2 on both blades, it is 6
It is 8.9%.

Next, when the pitch width is increased from 0.4 pm to 0.5 pm, as shown in ■ and ■, there is a difference in strength compared to the cases of ■ and ■ mentioned above, and the focus separation is also roughly 0.5 pm. 1
When expanded to βm''0.2 pm, it can be seen that there is a difference in the reflection intensity as shown in ■ and ■.

To summarize the second point, when the return light from the pair I/rack employing the recording method of this invention is received by the ζU photodetector for 2 minutes, in the case of ■ and ■, the mirror surface j:? If the reflectance is 100% in the case of B, then it will be reflected only by − force)I(
When there is +(H2), the reflection intensity on the side with pits is approximately 70%, and on the side without pits is approximately 90%. Also, it can be seen that when both have focus H, , H2, both become 70%.

Next, we will explain the ability to reproduce information recorded on paired trunks from such reflection intensity.

FIG. 6 shows the waveform when the detection signal is digitized based on the foul intensity, where CK is indicated as tj', 11.
li has two i1. The clock signals A and B synchronize with the i signal, A and B indicate the recorded information of a pair of digitized signals of the two series, and the diagonally lined area indicates the focus L.

A' and B' indicate the detection level of each of the two divided photodetectors, which corresponds to the pits H, , H in the table shown in Figure 5.
This is obtained from the relationship in 2.

A'-B' are the two detection levels A'.

The output when B' is input to the subtraction circuit, AD is the above-mentioned terminal l? i, BD The above is a digital value obtained by setting one side of the output A'-B' to 1/2 and adding it to the detection level B'.

As can be seen from this waveform diagram, the digital (i & A D has the same information as the recorded information A of one of the paired tracks 4111 is reproduced, and the digital value B
D is a reproduction of the digital information of the recorded information B of the other power.

The method of recording the independent information of the second system 11 as a pair track and reproducing it has been described above, but measures have been taken to improve the resolution and S/N of the detection system, If A becomes smaller, it becomes possible to further increase the recording surface density.

If it is combined with the already proposed multi-planting (4-haku), the recording surface density will be further increased and high-density recording and reproduction will be performed.

〔Effect of the invention〕

As explained above, the high-density recording (11 raw method) of the present invention records pit information in the width direction (water direction).
The original independent recorded information is read by dividing the track information into multi-track information, and detecting and processing the diffraction pattern of the return light reflected from this track information using the divided detectors.As a result, the recording surface density improves. 1) In 4j°, since the spot diameter obtained by a conventional semiconductor laser can be used for the spot during reproduction, there is an advantage that there is no particular increase in cost.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of return light detection using the Jinshupuru method.)
Figure '52 is a diagram showing the relationship between the irradiation spot of the first IA and the detected pattern, Figure 3 (a). (b) and (c) are diagrams showing the relationship between the pits of a poem whose recorded information is paired tracks and the detection pattern, and FIG. 4 is a schematic diagram when detecting paired track information according to the present invention.
The figure shows an explanation of when the diffraction pattern of paired track information is calculated by simulation 1.1. i:i's6 Figure is a waveform diagram when two independent tracks (I) are formed from paired track information. In the figure, H, , H2 are the focus points formed on one track, S is the spot on the playback side, and 107 is the laser beam: xl
! ,] 1 is a deflection beam splitter, 12 is a collimator lens, 13 is a 1/4 plate, 14 is an objective lens, 15 is a 2
A split light detection device is shown. Figure 1 Figure 2 Figure 3 j::/, i Figure 4

Claims (1)

[Claims] An optical disk [within a spiral globe formed with
Two or more pit strings, each with independent information, are recorded in parallel in a synchronized state, and while tracking the globe using one optical spot, the independent information is extracted from the diffraction pattern of the returned light. ．． High-abundance recording M raw method characterized by removing dust.