JPS63195828A - Automatic focus control system for optical disk device - Google Patents

Abstract

PURPOSE:To shorten a focus leading-in time at the time of turning on a power supply again by storing a signal value corresponding to the position of a lens at the time of turning off the power supply, correcting the signal value by a value corresponding to vertical movement and holding the lens position by the corrected signal value. CONSTITUTION:During the period of waiting at the off time of the power supply, automatic focus control and positioning control are executed to prepare operation at the time of turning on the power supply. In the automatic focus control, reflected light from a recording face 2 is separated from an emitted light beam by an optical system 6 and a distance between a recording/reproducing face and a focus to be stopped the position of the light source is detected by a photodetector 9. Then, a stopping lens 4 is driven by an actuator through an automatic focusing circuit 12, a changeover switch 13, a compensating circuit 14, an adder 15, and a driving circuit 16 so that said shifted distance is minimized. In the case of the positioning control, a shifted distance between an optical spot and the center of a track is detected by a photodetector 9 in the optical system 6 and a galvanomirror 7 through a control circuit 11 to control positioning. Thus, the lens is positioned near the track to rapidly execute starting processing.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an automatic focus control method for an optical disc device, and in particular, when the optical disc device is in a standby state, the light source is turned off, and then the light source is turned on and restarted. Related to automatic focus control method suitable for performing focus pull-in operation at high speed when starting up [Prior art] In an optical disk device, various signals from the recording film are detected if automatic focus control does not operate normally. Therefore, it is not possible to move on to the next operation, such as tracking. In addition, in order to shorten the startup time of data processing related to the information processing speed with the host device, it is always positioned in the track currently being executed or in the next track after completion.

As a prior art related to such an automatic focus control method, there is, for example, an invention described in Japanese Patent Application Laid-Open No. 58-85940.

[Problem that the invention seeks to solve]

In the above-mentioned conventional automatic focus control method for optical disk devices, for example, several to several optical disk devices are connected as a computer system, and required information is determined by reading the management information track on the recording surface of a specific optical disk. (That is, when the light spot is shifted toward a specific optical disk device, etc.), the operation of positioning the light spot on a certain track is always repeated in an optical disk device that is not needed.

Especially when using an optical disc fixed to a device,
After reading the label of the optical disc each time the power is turned on, the optical spot is always positioned only on a specific track. In such a case, there is a problem in that the guide groove portion or the recording portion of a particular track is slightly deteriorated, and the S/N ratio of read data is deteriorated, causing an error to occur.

The present invention has been made in view of the problems of the prior art described above, and has an object to provide an automatic focus control method for an optical disc device that is particularly suitable for preventing track deterioration and preventing the occurrence of repeated errors. It is said that

[Means for solving problems]

The automatic focus control method of the optical disc device of the present invention includes an optical system that includes a light source for generating a light beam, an optical head that focuses the light beam to form a light spot and irradiates it onto the optical disc, and a tracker for tracking the light spot. a moire control means for positioning the light spot by coarse control; a tracking control means for controlling an optical system to precisely position the light spot on the track; and a tracking control means for controlling the optical system to follow the vertical movement of the optical disc and focus it on the optical disc. This is applied to an optical disc device equipped with an automatic focusing means, and especially when the host device has not selected the optical disc, or has selected it but is in a standby state without an instruction for information processing, etc., the above light source is turned off to stop automatic focus control by the automatic focus means, and switch from accurate position control by the tracking control means to rough position control by the moiré control means, and move the optical head near the track where the light spot was positioned before the light source was turned off. is positioned, and then when the host device selects the optical disc or issues a command for information processing, etc., the automatic focusing means immediately starts and ends the focus pull-in operation.

[Effect]

According to the present invention, the light source of the light beam is first cut off when the device is not selected by the host device, or when it is selected but in a standby state without a command. Then, at the same time as the light source is turned off, the tracking control means is turned off, and the moiré control means having a linear scale for coarsely controlling the track position in the radial direction of the optical disk is turned on. position. Next, when the host device selects the optical disk device or issues a command, the automatic focusing means completes the focus pull-in operation in a short time. This focus pulling operation can be performed quickly by, for example, holding the lens at a position that takes into account the vertical movement caused by the rotation of the optical disk from the lens position in the focusing optical system when the light source is turned off. Specifically, it is sufficient to store a signal value corresponding to the position of the lens when the power is turned off, correct the vertical movement, and hold the lens position using the corrected signal value.

〔Example〕

The present invention will be described in more detail below with reference to embodiments shown in the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, showing a light spot alignment and positioning control system of an optical disc storage/reproduction device for recording and reproducing image or code information.

As shown in FIG. 1, an optical disk 1 serving as a medium has a recording/reproducing surface 2 and is rotated at a constant rate by a spindle motor 3. As shown in FIG. Information is recorded onto the optical disc 1 using a semiconductor laser 8.
After the light beam emitted from the optical system 6 passes through the optical system 6, it is focused on the recording surface 2 by the aperture lens 4, and the recording surface is physically deformed by the light spot. Reproduction of information on the optical disc 1 is performed by detecting reflected light from the light/spot by a photodetector 9 in the optical system 6.

The light spot irradiated onto the recording surface of the optical disc 1 is required to have extremely minute dimensions, and automatic focus control is necessary to control the light spot so that a constant range of light spot is always obtained even if the recording surface moves up and down. . This automatic focus control is performed as follows. That is, the optical system 6 separates the reflected light from the recording surface 2 from the emitted light beam, and the photodetector 9 detects the distance between the recording/reproducing surface and the focal point, which is the narrowed-down light spot position, to minimize this deviation. The automatic focus control circuit 12
, the changeover switch 13 , the compensation circuit 14 , the addition circuit 15 , and the drive circuit 16 , a current is passed through the actuator 10 to drive the aperture lens 4 . In this way, a light spot that follows the movement of the recording surface 2 of the optical disc 1 is formed.

Further, in order to position the light spot on the recording track on the recording surface 2, positioning control is required.

This positioning control is performed as follows. That is, the deviation between the light spot and the track center is detected by the photodetector 9 in the optical system 6 using the reflected light of the light spot, and the galvanomirror 7 is driven via the control circuit 11 to perform positioning control. .

A semiconductor laser 8 is used as a light source for the recording/reproducing and control system described above, and its light emission is controlled by a laser control drive circuit 17.

In addition to the output of the compensation circuit 14, the adder circuit 15 also includes the output of the compensation circuit 14.
The output of a D/A converter 18 that performs D/A conversion on the output of a control logic circuit 19 including registers and the like is input.

Further, a laser-on signal 21 is input as a control signal for the laser control drive circuit 17, and an autofocus servo signal 22 is input as a control signal for the changeover switch 13.

FIG. 2 is a time chart showing the operation of the embodiment shown in FIG. In FIG. 2, the timing signal 20 is
This is a signal that defines the timing for moving the focusing lens 4 produced in the control logic circuit 19, and is
The signal is processed by the A converter 18 and output from the D/A converter 8 in the form of a signal 23. Further, 24 indicates a lens position (proportional to the coil drive current), and indicates a state in which it moves up and down in accordance with the output signal 23 of the D/A converter 8. Also, signal 22 indicates an autofocus servo signal.

As shown in FIG. 2, when the timing signal 20 is output at time t1, the output signal 23 of the D/A converter 8 changes at time t2, and the lens position 24 moves up and down in response to this change. . As shown in the figure, the laser-on signal 21 is generated when the lens position 24 is sufficiently lowered (time t
At time t4, the autofocus servo signal 22 becomes "H" and starts the autofocus operation. Therefore, at time t4, the automatic focus control system sets the lens position 2 so that the vertical movement of the optical disc 1 is in focus.
4 control starts.

Next, at time t5, the laser-on signal 21 goes “L”.
The operation when the signal becomes "H" again at time t8 will be described. Note that the dotted line in the figure shows the operation according to the prior art, and the solid line shows the operation according to the zero invention.

At time t5, when the laser-on signal 21 is set to "L", the autofocus servo signal 22 also becomes "L", and the lens position 24 corresponds to the output signal 23 of the D/A converter 18. At this time, in the prior art, as shown by the dotted line, the output signal 23 of the D/A converter 18 maintains the in-focus position as it is, and when the timing signal 20 is output at time t6, from time t7 to tlo. The operation is completely the same as the operation from time t1 to time t4.

For this reason, it takes a long time from when the laser-on signal 21 becomes "H" to when the autofocus servo signal 22 becomes "H", which is the same as when starting up the optical disk device.

On the other hand, in this embodiment, when the laser-on signal 21 becomes "L" at time t5, the lens position 24 changes due to direct current from the reference surface on the disc receiving side to the recording surface, as shown by the solid line. The position is set by subtracting the alternating current fluctuation (for example, total vertical movement ±0.4 mm, AC subtraction 0.25 m) due to minute and vertical vibrations from the current lens position. That is, D/A
This means that the output signal 23 of the converter 18 is formed taking into account the above fluctuation.

In this state, the laser on signal 21 goes high at time t8.
”, the output signal 23 of the D/A converter 18 increases approximately by the amount of vertical vibration fluctuation of the optical disc 1, and then the autofocus servo signal 22 becomes “H” at time t9.
Automatic focus pull-in is started and the focus can be brought to a focused state immediately. Therefore, the restart time can be significantly shortened compared to the conventional technology.

Note that the output signal 23 shown by the solid line in FIG. 2 can be easily generated by known means.

Next, the control of the optical disc in the radial direction when the light beam source is cut will be described with reference to FIG. In FIG. 3, when the laser on signal 21 becomes "L" at time t5, the light spot positioned on a constant track with respect to the radial direction Galvano mirror shown in
7 is out of control. Therefore, if left as is, the light spot will shift outward or inward in the radial direction of the disk.

Therefore, at time t5, the moire servo-on signal 42 is set to "H" in order to perform rough tracking control using a linear scale (for example, 102.4 μm pinch). As a result, for example, for a track pinch of about 1.6 μm, the light spot is positioned near the track position before the laser-on signal 21 becomes “L”. That is, as shown by the solid line or dotted line in FIG. 3, it is controlled within one pitch of the linear scale.

In this way, by positioning it near the track being processed, it is possible to speed up the startup process from the host device on average.

〔Effect of the invention〕

According to the present invention, it is possible to significantly shorten the focusing time when re-inserting the light beam light source after cutting it off, so the light beam source of the device that is not in use is cut off and the light spot is placed on a specific track on the disk. It is possible to prevent deterioration of the recording film due to long-term irradiation, and it is possible to effectively prevent repeated errors.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a time chart showing the operation of the embodiment shown in FIG. 1, and FIG.
The figure is an explanatory diagram showing an example of position control of the optical head in the embodiment shown in FIG. 1. DESCRIPTION OF SYMBOLS 1... Optical disc, 2... Recording film surface, 4... Aperture lens, 11... Control circuit, 12... Automatic focus control circuit, 17... Laser control drive circuit, 18...
D/A converter, 19... control logic circuit.

Claims (1)

[Claims] 1. An optical system including a light source for generating a light beam, an optical head for focusing the light beam to form a light spot and irradiating it onto an optical disk, and a moire control means for positioning the light spot on a track by rough control; An optical disc device comprising a tracking control means for controlling an optical system to accurately position a light spot on a track, and an automatic focusing means for controlling an optical system to focus on the optical disc by following the vertical movement of the optical disc, When the host device has not selected the optical disk, or has selected it but is in a standby state without any instructions for information processing, etc., the light source is turned off, automatic focus control by the automatic focus means is stopped, and tracking is performed. Switching from precise position control by the control means to rough position control by the moiré control means, the optical head is positioned near the track where the light spot was positioned before the light source was turned off, and then the host device selects the optical disc or performs information processing, etc. An automatic focus control method for an optical disk device, characterized in that when a command is issued, an automatic focus means immediately ends a focus pull-in operation.