JPH0740365B2 - Optical disc device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical disc device, and in particular, there is a region where the focus of a light beam deviates from a predetermined position due to an obstacle such as a scratch on the disc. The present invention relates to a configuration suitable for reproduction in the case.

[Prior Art] Dedicated to reproduction of disc-shaped or cylindrical recording medium (hereinafter referred to as a disc) in which guide tracks are formed in linear or concentric circles, and address information indicating the guide track number is in forward order or recording is returned. One of the major features of the apparatus and the recording / reproducing apparatus is that an optical information reading section (hereinafter referred to as an optical head) can be moved in the disk radial direction to search for an arbitrary guide track on the disk at high speed. . As the search method, various methods have been proposed so far. For example, as described in JP-A-54-76104, the address difference between the guide track whose address is currently being read and the guide track targeted for retrieval is a threshold value Δ.
When it is larger than N, the optical head is moved in the direction of the target guide track at a high speed by the feed motor control, and when the address difference becomes the threshold value ΔN or less, the drive by the feed motor control is started and the tracking servo system is mainly operated. The number of pulses corresponding to the address difference is generated and the optical head is moved in the direction of the target guide track while moving the light spot by the track jump by tracking control. The test was performed and the above operation was repeated until the address difference disappeared.

[Problems to be solved by the invention]

The above-mentioned prior art is considered in the case where the focus of the light beam is deviated from a predetermined position during the search by the movement of the light spot in the feed motor control or the tracking control by the pulse output due to the obstacle such as a scratch on the disk. Didn't. For this reason, when a disk having a failure is used, there is a possibility that a search cannot be performed between normal tracks across this failure and that the disk cannot be used in the worst case. This becomes a problem particularly when the number of discs having the same contents is small, such as the discs recorded by the recording / reproducing apparatus.

It is an object of the present invention to enable a reproducing operation to be performed in a normal area with this obstacle even if the disc has an obstacle such that the light beam is out of focus from a predetermined position.

[Means for solving problems]

Therefore, in the present invention, when the focus of the light beam deviates from a predetermined position during the search in the movement of the light spot by the feed motor control or the tracking control,
The moving direction of the light spot immediately before this is held or stored, and the optical head is moved in the stored direction by the feed motor control, the focus of the light beam is again adjusted to a predetermined position, and then the address is read from the disk to read the target track. The target was achieved by testing the address difference between and and executing the search again.

[Action]

When the light beam is out of focus during the search in the movement of the light spot by the feed motor control or the pulse output, the moving direction of the light spot at this time is held or stored, and the feed head causes the light head to move the light beam. The light spot refocuses the light beam to a predetermined position while moving it in the direction in which the light spot was moving immediately before the focus was deviated from the predetermined position, that is, in the direction of the target track. When the light beam passes through a state where the focal point is deviated from the predetermined position and the light beam is again focused on the predetermined position, it means that the light beam is always located on the target track side over the obstacle of the disk. Therefore, thereafter, the target track can be searched by reading the address from the disk, verifying the address difference from the target track, and executing the search again.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is an explanatory diagram showing an example of a disc used in the present invention. As shown in the figure, the disk 2 has
In addition to the groove-shaped guide track 4 at the time of manufacturing, an address area 6 in which an address signal unique to each guide track is recorded and a mark 5 used for recording position alignment for each guide track
Are formed. Although only the spiral track 4 is shown in the figure for simplification of description, it goes without saying that this may be a concentric track.

FIG. 3 is an explanatory diagram showing the configuration of the optical head 1 for recording / reproducing used in the present invention. In the figure, the light beam from the laser diode 7 is a collimating lens 8
Then, it becomes parallel light, and polarized beam splitter 9 and 1/4 wavelength plate 1
Objective lens 12 taken by actuator 11 through 0
As a result, the light spot is narrowed down on the disc 2.

The reflected light from the disk 2 is again exchanged into parallel light by the objective lens 12, passes through the 1/4 wavelength plate 10, is reflected by the polarization reflection surface of the polarization beam splitter 9 and passes through the convex lens 13, and then is reflected by the mirror 14. Is divided into two, one of which is incident on the two-divided light receiving element 16 for detecting the focus error through the concave lens 15, and the other is incident on the two-divided light receiving element 17 for detecting the tracking error.

FIG. 4 is a block diagram showing an example of an optical recording / reproducing apparatus used in the present invention. In the figure, 2 is a disk, 18 is a detection photosensor for detecting the recording alignment mark 5, 19 is a waveform shaping circuit, and 20 is a disk so that one rotation of the disk 2 corresponds to one frame of the video signal. A disk motor drive circuit for controlling the motor 3, 21
Is a feed motor drive circuit for moving the optical head in the disk radial direction, 22 is a drive circuit of the laser 7 incorporated in the optical head 1, 23 is an IV conversion processing circuit, 24 is a preamplifier, and 25 is the optical head 1. A focus control circuit for controlling the focus of the light beam from the laser 7 to a predetermined position by controlling the actuator 11 incorporated in the disk, 26 is a tracking control circuit for making the light spot on the disk 2 follow the guide track 4, 27 is a Recording / playback signal processing circuit, 28 playback RF signal detection circuit, 29 address demodulation circuit, 30 recording control circuit, 31 system controller composed of microcomputer and memory, 32 input track address to be searched, etc. Keyboard.

An example of control when the disc is started will be described. The controller 31 makes the motor drive circuit control signal b high (or low) and causes the motor drive circuit 20 to rotate the disk motor 3. The motor drive circuit 20 adjusts the rotation speed and the rotation phase of the disk 2 to a predetermined state by the mark signal a obtained by detecting the recording position alignment mark 5 of the disk 2 by the photo sensor 18, and then outputs the motor lock signal c. Set high (or low). After confirming that the motor lock signal c has become high (or low), the controller 31 sets the focus control signal f to high (or low) to drive the laser 7 by the laser drive circuit 22 via the focus control circuit 25. Make it glow. The focus control circuit 25 uses the focus error signal j obtained by processing the incident light of the two-divided light receiving element 16 by the IV conversion processing circuit 23 and the preamplifier 24 while raising the actuator 11 incorporated in the optical head 1. After the light beam is focused on a predetermined position, the focus lock signal e is set to high (or low). After confirming that the focus lock signal e has become high (or low), the controller 31 searches for a predetermined track and ends the control for starting the disc.

Next, an example of the control in the case of performing the search at the time of starting the disk or the track specified by the keyboard 32 will be described with reference to the flowchart of FIG. 5 and the time chart of FIG. When searching for a predetermined search target track or a search target track input from the keyboard 32 (hereinafter referred to as target track), the system controller 31 first reads the address A ₀ of the track where the current light spot is located from the address demodulation circuit 29. , A process according to the address difference N−A _{0 from} the target track is performed. In the case of the present embodiment, when the absolute value of the address difference is | N−A ₀ | ≧ 100, the absolute value of the address difference | N−A ₀ | is preset in the feed motor drive circuit 21, and the address difference is N−A _{If 0} > 0, the moving direction signal g is set high (or low), and the address difference is N−A ₀
If <0, the moving direction signal g is set to low (or high), then the feed motor control signal d is set to high (or low), and the feed motor drive circuit 21 moves the optical head 1 in the target track direction at high speed. . The moving distance at this time can be obtained by counting the tracking error signal k detected each time the light spot crosses the track.

When the absolute value of the address difference is 1 <| N−A ₀ | <100, the absolute value of the address difference | N−A ₀ | is preset in the counter in the system controller 31, and the movement direction signal g
After setting, jump pulse h
The signal is output to the counter 26 at a cycle of about 2 msec until the counter reaches 0, and the tracking control circuit 26 causes the optical spot to jump one track at a time by the tracking error signal k and moves in the target track direction.

When the absolute value of the address difference is | N−A ₀ | = 1, one track is moved to reach the target track in the same manner as the normal normal reproduction.

The feed motor drive circuit 21 or the tracking control circuit
After the movement of the light spot by 26, the address A ₁ of the track where the light spot is located is read from the address demodulation circuit 29, and the tracking control circuit 26 or 1 is operated until the address difference from the target track becomes N−A ₁ = 0. The movement of the light spot due to the track movement is repeated to reach the target track. In FIG. 6, at time t _{0 to} t ₁ , the feed motor drive circuit 21
High-speed movement by t ₂ , t ₂ -t ₃ is the movement of the light spot by the track jump using the tracking control circuit 26, t ₁ -t ₂
And t _{3 to} t ₄ are the periods during which the address difference is tested,
t ₄ ~t ₅ (because of the movement to the disk outer peripheral direction in the case of the figure, the output of the jump pulse h for a track jump takes place not included) 1 track moved by the normal mode is.

The feed motor drive circuit 21 or the tracking control circuit
If the focus of the light beam is deviated from a predetermined position due to an obstacle such as a scratch on the disk 2 during the movement of the light spot by any of 26, the tracking error signal k cannot be normally obtained. For this reason, not only cannot the target track be searched, but the movement amount of the optical head 1 cannot be detected.
May go beyond the movable range and collide with a mechanical stopper.

Hereinafter, an example of search control in the case where there is a region where the focus of the light beam deviates from a predetermined position between the search start track and the target track due to an obstacle such as a scratch on the disk 2 will be described with reference to FIG. This will be described with reference to the explanatory diagram, the flowchart of FIG. 7 and the time chart of FIG.

The feed motor drive circuit 21 or the tracking control circuit
When the focus clock signal e becomes low (or high) during the movement of the light spot by 26, and it is detected that the focus of the light beam has deviated from the predetermined position, the system controller 31 executes the error processing. Start. First, when the feed motor drive circuit 21 is moving the optical head 1 at high speed, the feed motor control signal d is set to low (or high) to stop the optical head 1. Further, when the light spot is moving by the track jump using the tracking control circuit 26, the output of the jump pulse h is stopped. Next, the output of the movement direction signal g is held or stored in the memory in the system controller 31.
Then, the focus control signal g is set to low (or high) for T ₀ time to turn off the laser 7 and lower the actuator 11. Here, it goes without saying that the processing procedure may be changed before or after the movement of the optical head 1 is stopped after the focus control signal g is set to low (or high).

After the time T ₀ has elapsed and the actuator 11 has sufficiently descended, the movement direction signal g is set to the held or stored output, and the feed motor drive circuit 21 is provided with a predetermined value for moving the optical head 1 at a low speed. By presetting and setting the feed motor control signal d to high (or low), the optical head 1 is moved in the direction in which the light spot is moving immediately before the focus of the light beam deviates from the predetermined position, that is, in the target track direction. , The focus control signal f is set to high (or low) to activate the focus control circuit 25,
It waits until the light beam is focused again at a predetermined position, that is, the focus lock signal e becomes high (or low). If the focus signal e does not become high (or low) within the time T _{1, the} focus control signal f is made low (or high) again for the time T ₀ , the focus control circuit 25 is stopped, and the actuator 11 is lowered. The operation of setting the focus control signal f high (or low) again and operating the focus control circuit 25 is repeated.
In this embodiment, the actuator 12 is arranged so that the objective lens 12 does not hit the disk 2 when the actuator 11 moves up.
A limiter is applied to the drive voltage of 11.

When the focus lock signal e is detected to be high (or low), the light spot crosses the obstacle of the disk 2 from the search start track to the target track side, as shown at point c in FIGS. 1 and 8. positioned. Therefore,
At this position, the address A ₀ is read from the address demodulation circuit 29, the address difference from the target track N is verified, and the target track can be searched by controlling the search of the target track.

In the present embodiment, it is detected that the focus lock signal e becomes low (or high) when the focus of the light beam deviates from a predetermined position during the movement of the light spot by the feed motor drive circuit 21 or the tracking control circuit 26. After that, the focus control signal f is set to low (or high) for T ₀ time, and then the focus control signal f is set to high (or low) again to send the focus control circuit 25 to the motor drive circuit 21 by presetting a predetermined value to send. Motor control signal d
Is set to high (or low) to move the optical head 1 at a low speed, but immediately after detecting that the focus of the light beam deviates from the predetermined position, a predetermined value is preset in the feed motor drive circuit 21 to Of course, it does not matter even if the head 1 is moved at a low speed. Further, it is of course possible to change the moving speed of the optical head 1 or temporarily stop it.

〔The invention's effect〕

According to the present invention, when the focus of the light beam deviates from the predetermined position during the movement of the optical head by the feed motor control in the search of the target track or the movement of the light spot in the tracking jump by the tracking control,
While the optical head is moving in the direction in which the light spot was moving immediately before the focus of the light beam deviated from the predetermined position, that is, the direction of the target track, the focus of the light beam was again adjusted to the predetermined position and the target track was searched again. Therefore, if there is an area where the focus of the light beam deviates from the predetermined position due to an obstacle such as a scratch on the disk, it is possible to search even between arbitrary tracks sandwiching this obstacle area. effective.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an example of the operation of an optical head according to an embodiment of the present invention, FIG. 2 is an explanatory diagram showing an example of a disc, and FIG.
FIG. 4 is an explanatory view showing the structure of an optical head, FIG. 4 is a block diagram showing an example of an optical recording / reproducing apparatus which is an example of an object of the present invention, and FIG. 5 is a flow chart showing an example of a normal search direction. 6 is a timing chart showing an example of the operation according to the flowchart of FIG. 5, FIG. 7 is a flow chart showing an embodiment of the search method according to the present invention, and FIG. 8 is an example of the operation according to the flowchart of FIG. It is a time chart. 1 ... Optical head, 2 ... Disc, 3 ... Disc motor, 4 ... Guide track, 5 ... Recording alignment mark, 6 ... Address area, 7 ... Laser diode,
16: 2-division light receiving element for focus error detection, 17: 2-division light receiving element for tracking error detection, 21 ... Feed motor drive circuit, 25 ... Focus control circuit, 26 ... Tracking control circuit, 29 ... Address Demodulation circuit, 31 ... Controller, d ... Feed motor control signal, d, e ... Focus lock signal, f ... Focus control signal, g ...
Moving direction signal, h ... jump pulse, j ... focus error signal, k ... tracking error signal.

Claims (3)

[Claims] 1. Focus control means for focusing a light beam on a disk, movement control means for moving the beam in a direction including at least a radial component of the disk, and detecting whether or not the light beam is in focus. An optical disk device having a detection means, comprising a storage means for holding or storing the moving direction of the light beam, and when the detection means detects a focus deviation during the movement of the light beam, the focus deviation is detected. Using the signal from the previous storage means as at least an operation direction signal, the movement control means moves the light beam forward in the same direction as before the focus shift, and the focus control means brings the light beam into the focused state again. An optical disc device characterized by a structure for returning. 2. The movement control means and the focus control means,
The optical disc device according to claim 1, wherein the optical disc device is configured to perform a forward movement operation and a focusing operation of the light beams overlapping with each other in time after the focus shift. 3. The movement control means according to claim 1, wherein the movement control means performs a forward movement operation of the light beam at a speed lower than that at the time of focusing when the focus is deviated. Optical disc device.