JPH011122A - Crosstalk removal circuit in optical playback device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a zero-stroke elimination circuit in an optical reproducing device, and in particular, to a zero-strike removal circuit for an optical reproducing device, and in particular to a zero-stroke elimination circuit for an optical reproducing device. The present invention relates to a circuit for removing 0-stoke included in a reproduced signal of a main light beam when reproducing a kite recorded information signal.

2. Description of the Related Art As one of the apparatuses for reproducing recorded edge information signals of an optical disc as an information recording medium using a light beam, a device having ten three light beams (light spots) is conventionally known. In such an optical reproducing device, the information signal reproducing 1
Two sub-light beams are arranged so as to irradiate the three-light beams in front and behind in the track scanning direction and in opposite directions in the track width direction.

The main light beam mentioned above is the 0th-order diffracted light obtained by the diffraction grating, and the two sub-light beams mentioned above are the +1st-order diffracted light and the 11th-order can light similarly obtained by the diffraction grating.

According to such an optical reproducing device using three light beams, information signals are reproduced by the above-mentioned main light beam (0th order diffracted light), and astigmatism is performed by the reflected light of the main light beam (0th order diffracted light). A focus error signal can be detected using the aberration method, and tracking control of the three-spot optical head can be performed based on the reflected light of the two sub-light beams (±first-order diffracted light).

Problems to be Solved by the Invention However, in the reproduced information signal from the track to be reproduced, which is obtained by irradiating the main light beam onto the optical disk and detecting the reflected light, there are It also contained some crosstalk components reproduced as crosstalk from the track, which degraded the quality of the reproduced signal.

The present invention has been developed in view of the above points, and an object of the present invention is to provide a crosstalk removal circuit in an optical playback device that can substantially remove crosstalk components.

Means for Solving the Problems The crosstalk removal circuit in the optical reproducing apparatus of the present invention is capable of eliminating crosstalk components including crosstalk components from adjacent tracks, which are reproduced from a track to be reproduced on an information recording medium by a main light beam. delay means for time-aligning one reproduction signal and a second reproduction signal reproduced from tracks adjacent to one or both sides of the track to be reproduced by the plurality of sub-light beams; and a second reproduction signal from the delay means. and subtracting means for adjusting the level of the reproduced signal and subtracting it from the first reproduced signal from the delay means.

The main beam for reproduction which is the action O-order diffracted light and the plurality of control sub-light beams which are diffracted lights other than the 0th order are recorded in the information record 8a! The first light irradiated onto the body and obtained from the reflected light (or transmitted light)
The second reproduced signal is time-synchronized by correcting the reproduction time deviation due to the difference in the position of the beam spot by the delay means.

Thereafter, the first and second reproduced signals taken out from the delay means are each subjected to relative level adjustment and then subtracted, so that the crosstalk component in the first reproduced signal becomes the same as that of the second reproduced signal. It is approximately canceled out and removed. Therefore, the 16th reproduction signal (reproduction information signal) in which the crosstalk component is significantly reduced is taken out from the delay means.

Embodiment FIG. 1 shows a block system diagram of an embodiment of the present invention. In the figure, 1 is an input terminal for a reproduced video signal reproduced using the main light beam for reproduction from a track to be reproduced on the optical disk, and 2 and 3 are input terminals for inputting a reproduced video signal from tracks adjacent on both sides of the track to be reproduced, respectively. This is an input terminal for reproduced video signals that are reproduced separately as crosstalk using two sub-light beams for control.

Here, the above-mentioned main light beam and two control sub-light beams will be explained in more detail with reference to FIG. 2.

In FIG. 2, M indicates a beam spot on the optical disk by the main light beam for reproduction, and 81 and S2 indicate beam spots on the optical disk by the two control sub-light beams, respectively.

The beam spot S1 is arranged in front of the beam spot M of the main light beam in the scanning direction, and the beam spot S1
2 is arranged behind the beam spot M in the scanning direction, and the beam spots s1 and S2 are respectively arranged at positions shifted from the beam spot M by equal distances in the upper direction perpendicular to the scanning direction and in the opposite direction. ing. These three beam spots M, 81, and S2 always maintain their relative positional relationship, and the beam spot M by the main light beam is set on the track to be reproduced (here, a large number of bits 14 are intermittent) by known means. As is well known, the reflected main light beam forms a 1° beam spot M that is tracked so as to scan the 1° beam spot M, and is photoelectrically converted by a light-receiving element, demodulated, and output from the track to be reproduced. It is converted into a reproduced video signal and sent to the front 2 input terminal 1.

Similarly, reproduced video signals of adjacent tracks on both sides of the track to be reproduced are separately inputted to input terminals 2.3 from the reflected sub-light beams forming beam spots 81 and 82. When this reproduced video signal is recorded on an optical disk, for example, a frequency-multiplexed signal consisting of a frequency-modulated luminance signal and a low-frequency converted carrier color signal that occupies an empty frequency band below the frequency-modulated luminance signal is recorded. , the FM-demodulated reproduced luminance signal, or the reproduced carrier color signal returned to the original band, or both of the reproduced signal processing systems may be provided with the circuit of this embodiment.

As mentioned above, even if the beam spot M by the main light beam follows and scans on the track to be reproduced by tracking control, the beam spot M may appear in the input reproduced video signal of the input terminal 1, albeit slightly. Adjacent tracks on both sides of the track to be reproduced (i.e., the first adjacent track recorded as a row of bits 13 in which the video signal is intermittent, and the second adjacent track recorded as a row of bits 1°5 in which the video signal is intermittent) Contains crosstalk components from adjacent tracks). This crosstalk component is the first
A first crosstalk component is obtained by reproducing the recorded edge video signal of the adjacent track as crosstalk, and a second crosstalk component is obtained by reproducing the recorded edge video signal of the second adjacent track as crosstalk.

On the other hand, among the beam spots S1 and S2 formed by the control sub-light beams, the reproduced video signal obtained from the sub-light beams that are reflected after forming Sl is the first crosstalk component corresponding to the first crosstalk component. The reproduced video signal from one adjacent track occupies most of the proportion, and the reproduced video signal from the track to be reproduced is largely included. On the other hand, S
Most of the reproduced video signal obtained from the n1 light beam formed and reflected by the second crosstalk component is the reproduced video signal from the second adjacent 1 to rack, which corresponds to the second crosstalk component, and A small amount of the reproduced video signal from the track to be reproduced is included. Therefore, in the present invention, the crosstalk components in the reproduced video signal of the main light beam are canceled out by the reproduced video signals of these two sub-light beams.

Here, as shown in FIG. 2, among the three beam spots M, S1, and S2, Sl scans d by a time 2τ ahead of S2, and M scans a time τ ahead of S2. scan the position.

Returning to FIG. 1 again, the input reproduced video signal (including crosstalk components) at the input terminal 1 is delayed by a time τ by the delay circuit 4, and the input reproduced video signal at the input terminal 2 is delayed. By circuits 5 and 6, each time τ is 2 in total.
τ will be extended soon.

Here, the optical disc uses a constant angular velocity system (CA) where the number of rotations is constant.
(V system), the linear velocity differs depending on the position in the radial direction of the optical disc, so each delay time τ of the delay circuits 4° 5 and 6 is adjusted by the control signal from the input terminal 7 to the beam spot M. .

The positions of S1 and S2 are variably controlled so that they gradually become smaller as they move away from the center of the optical disc.

On the other hand, when the optical disc is of the CLV type with a constant linear velocity, the linear velocity is always constant regardless of the radial position of the optical disc.
Each delay time τ of delay circuits 4.5 and 6 is always fixed to a constant value by the l signal.

A reproduced video signal from the track to be reproduced taken out from the delay circuit 4, a reproduced video signal from the first adjacent track taken out from the delay circuit 6, and a reproduced video signal from the second adjacent track taken out from the input terminal 3. The signals are time-synchronized, and the reproduced video signals of the first and second adjacent tracks are added together by an adding circuit 8.

The reproduced video signal taken out from the adder circuit 8 is adjusted to level 3 by the level adjuster 9 to maximize the amount of crosstalk removed.
After being adjusted, it is supplied to a subtraction circuit 10, where it is subtracted from the reproduced video signal from the delay circuit 4. As a result, the first and second crosstalk components mixed in the video signal reproduced from the track to be reproduced from the delay circuit 4 in the subtraction circuit 10 are reduced to the same level! It is canceled out and removed from the added reproduced video signal corresponding to the first and second crosstalk components from aiW9. Therefore, a reproduced video signal reproduced from the track to be reproduced and from which crosstalk components have been removed is output from the reduction circuit 10 to the output terminal 11.

Next, a further embodiment of the circuit of the present invention will be described with reference to FIG. In FIG. 3, the same components as those in FIG. 1 are designated by the same reference numerals, and their explanations will be omitted. In FIG. 3, the reproduced video signal from the first adjacent track taken out from the delay circuit 6 is supplied to the level adjuster 17, and the reproduced video signal from the second adjacent track from the input terminal 3 is level adjusted. is supplied to the vessel 18.

The arithmetic circuit 19 converts the reproduced video signal containing the first and second crosstalk components from the delay circuit 4 into reproduced signals corresponding to the first and second crosstalk components from the level adjusters 17 and 18. A subtraction operation is performed to subtract each video signal. The level adjusters 17 and 18 adjust the level of the reproduced video signal from the adjacent track in the arithmetic circuit 19 so that the level of the reproduced video signal from the adjacent track is approximately the same as that of the first and second crosstoe components in the reproduced video signal from the delay circuit 4. .

Therefore, from the arithmetic circuit 19 to the output terminal 11, a reproduced video signal reproduced from the track to be reproduced and whose crosstalk components have been canceled out and removed is taken out. In this way, this embodiment has a configuration in which level adjustment is performed separately for reproduced video signals that are reproduced separately using two sub-light beams from two adjacent tracks. Compared to the embodiment shown in FIG. 1, in which the level is adjusted all at once after adding and combining the reproduced video signals that are reproduced separately using the present invention, the level adjustment for eliminating crosstalk can be performed with higher precision.

Effects of the Invention As described above, according to the present invention, since the reproduction signals of the plurality of sub-light beams are reduced to a level suitable for the reproduction signal of the main light beam, reproduction with substantially eliminated crosstalk components can be achieved. It is possible to obtain a video signal, thereby improving the quality of the reproduced signal, and it is also possible to remove crosstalk using the existing sub-beam for control without preparing a special beam for crosstalk removal. It has the following features.

[Brief explanation of the drawing]

FIGS. 1 and 3 are block diagrams showing respective embodiments of the present invention, and FIG. 2 is a diagram showing an example of a beam spot on an optical disk. 1... Playback video signal input terminal using main light beam, 2.
3... Reproduction video signal input terminal by sub-light beam, 4.
5.6...Delay circuit, 7...Delay time control signal input terminal, 8...Tightening circuit, 9.17.18...Level adjuster, 10...Subtraction circuit, 11...・Output terminal, 1
9... Arithmetic circuit. Patent applicant: TIATSUKU Co., Ltd. Figure 1 Figure 2 ←-8-#J

Claims (1)

[Claims] Reproduction by irradiating an information recording medium with a reproduction light beam, which is 0th-order diffracted light emitted from a light source through a diffraction grating, and a plurality of control sub-light beams, which are other diffracted lights. In an optical reproducing device that obtains an information signal from a reproduction signal of the main light beam, a first information signal including a crosstalk component from an adjacent track, which is reproduced from a track to be reproduced on the information recording medium by the main light beam, is provided. delay means for time-aligning the reproduced signal and a second reproduced signal reproduced from tracks adjacent to one or both sides of the track to be reproduced by the plurality of sub-light beams; subtracting means for level-adjusting the second reproduced signal and subtracting it from the first reproduced signal extracted from the delay means; A crosstalk removal circuit in an optical playback device, characterized in that the circuit is configured to extract the first playback signal that has been substantially canceled out.