JPS61151843A - Optical memory disk - Google Patents

Abstract

PURPOSE:To attain the tracking control easily and with high accuracy by deforming the boundary between both side walls of a groove for recording track and recording tracking detection signals f1 and f2 independently of each other. CONSTITUTION:The half-width bits 8a and 8b which are modulated by tracking detection signals f1 and f2 are formed on the side walls 7a and 7b of a groove 4 provided for recording track. In a reproduction mode a reading laser beam 6 is irradiated to the entire bottom area of the groove 4. Then the reproduction signal A is supplied to the band pass filters BPF11 and 12 having pass frequencies F1 and F2 respectively. Thus the signals f1 and f2 are extracted. Then a tracking error signal TE is obtained from the difference of wave detection outputs.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an optical memory disk in which information is recorded and reproduced optically, and particularly to an optical memory disk in which reliable tracking control can be easily obtained.

<Prior art> An optical memory disk has an optical recording/reproducing film in which an optical recording medium is adhered in a thin film form on one side of a disc-shaped transparent substrate, and the optical recording/reproducing film is coated with an optical recording medium according to recorded information. By irradiating a modulated laser beam, information is recorded by deforming or discoloring it into a bit shape, and during playback, the amount of light reflected from the readout laser beam against the recording track changes depending on the recorded information. This is for reading. This optical memory disk has attracted particular attention in recent years because it can perform high-density recording by using a laser beam.

FIG. 3 is a plan view showing an example of an optical memory disk commonly used in the past, and FIG. 4 is a sectional view of a main part of the optical memory disk shown in FIG. 3. Here, optical memory disk 1
The device has a disk-shaped substrate 2 made of a material that is transparent and has excellent heat resistance, and a center hole 3 into which a rotational coupling portion is fitted is provided at the center of rotation. Further, the surface of this substrate 2 has a depth T of 0.05 to 0.11.3.
m, width W is 0.4 to 0.6 μs, pitch P is 1.6 to 2
．． The grooves 4 for recording tracks are provided in a spiral or concentric manner at about 6-degrees. Then, an optical recording medium is deposited in a thin film on the surface of the substrate 2 where the grooves 4 are formed, so that optical recording and reproduction ll! 5, and a protective layer (not shown) is laminated on the back side thereof.

In the optical memory disk constructed in this way, as shown by the one-dot line 6, the groove portion is irradiated from the exposed surface side of the substrate 2 along the groove 4 with a laser beam 6 modulated by recorded information. Recording information is recorded as a bit string by deforming or discoloring the optical recording/reproducing film 5 adhered to the optical recording/reproducing film 5 into a pit shape. Further, when reproducing recorded information, a readout laser beam is irradiated along the groove 4 in the same way as during recording, and the recorded information is read out using changes in the intensity of the reflected light.

In this case, what is important during recording and reproduction is to perform tracking control so that the laser beam is always located at the center of the groove 4. Tracking control in this case detects deformation due to tracking deviation by detecting changes in the light receiving pattern of the reflected light of the laser beam used during recording and playback, for example, by dividing the light into four parts, and detects the deformation due to tracking deviation. Control is performed using the component as a tracking error signal.

<Problems to be Solved by the Invention> However, in the optical memory disk having the above configuration, when surface wobbling occurs due to rotation of the optical memory disk, the receiving pattern of reflected light changes due to this surface wobbling. However, there is a problem in that the tracking error signal includes a component due to surface runout, making tracking control unstable.

Means for Solving the Problems In order to solve these problems, the optical memory disk according to the present invention is capable of tracking detection by deforming the boundaries on both side walls of the groove provided for the recording track. Signal f1. f2 are recorded independently from each other.

In the optical memory disk configured and constructed in this way, during reproduction, the recording track area including both side walls of the groove is irradiated with a laser beam spot, so that the reproduced signal detected by the reflected light is are the tracking detection signals fl, f
2 will be included at a level depending on the trace position of the laser beam relative to the recording track area. Therefore,
Tracking detection signal fl included in this reproduced signal
.

By determining the level difference of f2, it is possible to reliably obtain a tracking error signal that is not affected by the surface runout of the optical disk, and by controlling tracking and king using this tracking error signal,
Highly accurate tracking control can be performed.

<Embodiment> FIG. 1 is a sectional view of a main part showing an embodiment of an optical memory disk according to the present invention, and the same parts as in FIG. 4 are indicated using the same symbols. In the figure, 7a and 7b are the side walls of the groove 4 provided for the recording track 2. The boundary portion between the g14 walls 7a and 7b receives tracking detection signals f1. Deformation according to f2, that is, tracking detection signals fl,
Half-width pitches 8a and 8b modulated by f2 are formed. 9 is a pit of recorded information written along the center portion of the groove 4.

In an optical memory disk configured in this way, for example, when a reading laser beam 6 is irradiated to cover the entire bottom of the recording track groove 4 during playback, the reflected light will cause the groove 4 to be exposed. This includes tracking detection signals f, , f2 due to boundary change states of the side walls 7a and 7b, that is, half-width pits 8a and 8b. Therefore, as shown in FIG. 2, for example, after the reproduction signal A read by an optical head (not shown) is amplified in the buffer amplifier 9, the passing frequency becomes Fl.

Bandpass filter 1 each set to F2
1.12, tracking detection signals fl and f2 are extracted. And this tracking detection signal f1.

When f2 is detected and smoothed in the detection circuits 12 and 13, a laser beam 6 and a side wall 7a are generated.

DC tracking signal Df1 indicating the relationship with half-width pits 8a and 8b provided in 7b by signal level
, Df2 are output. In other words, when the irradiation spot of the laser beam 6 is located at the center of the groove 4, 1I8r
The levels of the current tracking signals Df1 and Df2 are the same, and when the radiation spot of the laser beam 6 deviates from the center of the groove 4 in the left-right direction, the level of the DC tracking signal Df+ or Df2 corresponding to this direction of deviation increases, and The other one! The level of current tracking signal Df2 or Df+ decreases. Therefore, the detection circuit 12.
DC tracking signal Df+ output from 13,
By supplying Df2 to the operational amplifier 14 and finding the difference between both signals, a tracking error signal TE indicating the amount of tracking deviation is obtained, and the polarity of this tracking error signal TE indicates the direction of deviation. For this,
By supplying the tracking error signal TE to a tracking control circuit (not shown), highly accurate tracking control can be performed by feedback control. Here, for example, if surface wobbling occurs in the optical memory disk 2, the influence of this surface wobbling will be caused by both DC tracking signals D.
It appears commonly in L+ and D f2.

However, the tracking error signal TE is
4, both DC tracking signals Dfl and Df2
Since it is obtained by determining the difference between the two, the influence of surface runout is easily canceled out, and only the tracking error signal is extracted.

In the above embodiment, only the operation during reproduction was explained, but it goes without saying that it is also used during recording.

<Effects of the Invention> As explained above, in the optical memory disk according to the present invention, the tracking signals f1 and f2 can be changed by deforming the boundary portions on both side walls of the groove provided for the recording track. Since they were recorded independently from each other, the tracking signals f1.
By obtaining the difference signal of f2 and using it as a tracking error signal, the influence of surface runout is removed and highly accurate tracking control can be easily obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part showing an embodiment of an optical memory disk according to the present invention, FIG. 2 is a circuit diagram showing an example of a tracking error detection circuit, and FIG. 3 is a plan view showing an example of a conventional optical memory disk. FIG. 4 is a sectional view of a main part of the optical memory disk shown in FIG. 3. 2... Substrate, 4... Groove, 5... Optical recording and reproducing film, 7
a. 7b...side wall, 8a, 8b...half width bit. Figure 1 Figure 2

Claims (1)

[Claims] (1) An optical recording and reproducing film is formed by depositing an optical recording medium on the surface of a substrate having grooves for recording tracks, and the groove portion is used as an information recording track area and is irradiated with a laser beam modulated by recorded information. In an optical memory disk in which information is optically recorded on the optical recording/reproducing film in the portion, and the recorded information is reproduced by detecting a change in the amount of reflected light of a reproduction laser beam irradiated to the information recording track area, An optical memory disk characterized in that tracking signals f_1 and f_2 of different frequencies are recorded independently from each other by deforming boundary portions on both side walls of a groove.