JPH01100736A - Optical disk device - Google Patents

Abstract

PURPOSE:To realize stable coarse feed control and coarse retrieval control by controlling the position of an objective lens in the radius direction of an optical disk at almost the same position as that of an optical disk device at the time of starting the operation. CONSTITUTION:A latch means 33 which inputs from a position detecting means and latches a position signal representing the relative position of the objective lens 5 for an optical head and along the radius direction of the optical disk 7 in the free state (wherein it is suspended freely by an actuator without being affected by an external force) of the objective lens 5 with respect to the radius direction of the optical disk 7 at the time of starting the operation of the optical disk device is provided. And the position signal latched by the latch means 33 is used as a reference signal. Therefore, it is possible to control the position of the objective lens 5 in the radius direction of the optical disk so that the objective lens 5 can always take almost the free state. In such a way, it is possible to improve a coarse feed capacity and a coarse retrieval capacity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical disc device, and in particular, an optical disc device that is characterized by the method of obtaining a reference signal during coarse movement control of an optical head and rough search control for a desired track. It is related to.

[Conventional technology]

A method for detecting the position of an objective lens in a conventional optical disc device is disclosed in Japanese Patent Application Laid-open No. 57-169933 and Japanese Patent Application Laid-open No. 61-2.
It is disclosed in Japanese Patent No. 76137 and the like. Further, coarse movement control of an optical head performed by detecting the position of an objective lens during disk reproduction is disclosed in Japanese Patent Laid-Open No. 169933/1983.

[Problem that the invention seeks to solve]

In optical disc devices, various systems have been adopted and put into practical use as actuators capable of movably suspending an objective lens in the direction of its optical axis and in the radial direction of the optical disc, and driving it in those directions. However, in any actuator, the objective lens is movably suspended (supported) at least in the radial direction of the optical disc by support means such as rubber, plate springs, coil springs, etc. During coarse movement of the optical head and coarse search, the supporting device is brought into a free state in the radial direction of the optical disk by applying an appropriate current to a coil provided in the actuator to drive the objective lens in the radial direction of the optical disk. It is desirable to control the conditions so that they are almost the same.

1. However, the objective lens position signal obtained from the objective lens position detection means fluctuates due to the deformation of the above-mentioned support device over time, the position shift of the photodetection means shown in the conventional example over time, and the like. This variation over time is generally unavoidable, and as a result, during coarse feed control and coarse search control, the support means that supports the objective lens is not always in a free state in the radial direction of the optical disc, but in a deformed state due to external force. Since the data is retained, coarse movement feed performance and coarse search performance deteriorate.

In the conventional example, no consideration is given to temporal fluctuations in the position signal of the objective lens.

An object of the present invention is to maintain a stable coarse position even if the position signal of the objective lens changes over time, by keeping the support means for supporting the objective lens in almost the same state as in the free state during coarse movement feed control and rough search control. The object of the present invention is to provide an optical disc device that enables dynamic forwarding control and coarse search control.

[Means for solving problems]

The above purpose is to detect the position of the objective lens when the objective lens is in a free state in the radial direction of the optical disc (a state in which it is freely suspended by the support means without receiving any external force) at the start of the operation of the optical disc device. The position signal obtained from the means is stored as a reference signal and held until the end of the operation of the optical disk device, and coarse movement feed control,
This is achieved by controlling the position of the objective lens in the radial direction of the optical disk to approximately the same position as when the optical disk device starts operating, using the reference signal during rough search control.

[Effect]

In the present invention, it is possible to control the position of the objective lens in the radial direction of the optical disk so that the objective lens is always in a position where it can be in a substantially free state, thereby improving coarse movement feeding performance and coarse search performance. becomes possible.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4. FIG. 1 is a block diagram showing an optical disc device as an embodiment of the present invention, FIG. 2 is a timing chart of signals in the main parts of FIG. 1, and FIG. 3 is a main part of the optical disc device shown in FIG. 1. 4 is a plan view showing the details of the 1st
FIG. 2 is an explanatory diagram of the operating principle of the photodetector shown in the figure.

First, the main parts of the optical disk device related to the present invention will be explained with reference to FIG.

In FIG. 3, a laser beam 2 emitted from a semiconductor laser 1
The light passes through a diffraction grating 3 and a beam splitter 4 and is focused by an objective lens 5 onto an optical disk 7 rotated by a motor 6. The laser beam reflected by the optical disk 7 passes through the objective lens 5, is reflected by the beam splitter 4, passes through the cylindrical lens 8, and is focused onto the photodetector 9. The objective lens 5 is attached to an actuator IO having a known configuration so that it can be driven in the direction of its optical axis and in the radial direction of the optical disk 7, and the actuator IO is provided with a focus drive coil 11 and a tracking drive coil 12. The entire optical head 13 is screwed together with a feed screw 15 rotated by a slider motor 14, and by rotating the slider motor 14, the optical head 13 can be moved in the radial direction of the optical disk 7.

As shown in FIG. 4, the photodetector 9 has six light receiving areas 9a to 9.
It consists of 9f. Others 16°17.18.
19 is an adder, and 20.21°22 is a subtracter.

A focus error signal 23 is detected from the difference between the output sum of areas 9a and 9C and the output sum of areas 9b and 9d, and a tracking error signal 2 is detected from the output difference between areas 9e and 9f.
4 is detected. Furthermore, the output sum of the area 9a and the area 9b,
Based on the difference between the output sums of the area 9C and the area 9d, a position signal 25 corresponding to the relative position of the objective lens 5 with respect to the optical head 13 along the radial direction is detected based on the same principle as in the conventional example described above. Ru.

The focus error signal detection method described above is based on an astigmatism method, and the tracking error signal detection method is based on a multi-spot method, both of which are widely used in practical use and will not be described in detail.

Next, the configuration and operation of an optical disc device as an embodiment of the present invention will be explained with reference to FIGS. 1 and 2. Note that the horizontal axis of the timing chart shown in FIG. 2 is time (1), and the vertical axis is the voltage level of each signal.

In FIG. 1, 5 is an objective lens, 9 is a photodetector, and 12
is a tracking drive coil, 14 is a slider motor, 1
6.17 is an adder, 20, 21°36 is a subtracter, 26 is a system control circuit, 28 is a focus servo circuit, 30
is an A/D converter, 33 is a latch circuit, and 34 is a D/A
Converter, 37.40.49 is a phase compensation circuit, 38,
39, 41, and 48 are switches, 42 is a slider voltage generation circuit, and 46.47 is a drive circuit.

A focus-on signal 27 is output from the system control circuit 26 and input to the focus servo circuit 28. The focus drive coil 11 shown in FIG. 3 and the focus error signal 23 shown in FIG. 4 are connected to the focus servo circuit 28.The objective lens 5 is moved up and down in the direction of its optical axis by a well-known focus pull-in operation. At the time TI when the just focus position is reached, a focus servo loop (not shown) is turned on.

At the same time, the focus lock signal 2 shown in FIG.
9 is output from the focus servo circuit 28. A position signal 25 of the objective lens 5 obtained by calculating the output signal of the photodetector 9 is input to an A/D converter 30.

On the other hand, the system control circuit 26 starts operating the A/D converter 3 immediately after the focus lock signal 29 becomes high level.
It continues to monitor the output 31 of 0, and outputs a latch timing signal 32 if, for example, the output 31 continues to have the same value three times or more. If the latch circuit 33 is configured to latch the input signal at the rising edge of the latch timing signal 32, the output of the A/D converter 30 will be latched at time T2 in FIG. The output, that is, the output of the latch circuit 33 is input to a D/A converter 34 and converted into an analog signal 35.

By the way, the tracking loop control signal 44, which is a control signal for the switch 38 and the switch 48, is at a low level at time T, as shown in FIG. 2, so that the switch 38 and the switch 48 are turned off. Therefore, the slider servo and tracking servo are off, and only the focus servo shown in the figure is on at times T to T3.

The latch circuit 33 described above is connected to the objective lens 5 in this state.
This means that a signal obtained by digitizing the position signal 25 along the radial direction of the optical disc 7 is latched. This position signal 25 is held until the operation of the optical disk device is completed.

Next, a tracking servo during normal reproduction of the optical disc 7 and a slider servo (coarse feed) for moving the optical head 13 in the radial direction of the optical disc 7 by the motor 14 as the optical disc 7 rotates will be described.

Time T required for the D/A converter 34 to input the output signal of the latch circuit 33 and convert it into an analog signal 35
At time T3, when time d has elapsed, the tracking loop control signal 44 becomes high level, and the switch 3,
The switch 48 is turned on, and the tracking servo and slider servo are turned on. In this state, the difference between the output 25 of the subtracter 20 and the output 35 of the D/A converter 34 is taken by the subtracter 36, and the output is phase compensated by the phase compensation circuit 37, and then sent through the switch 38 and the switch 39. The signal is input to the drive circuit 47 and drives the slider motor 14. As a result, a slider servo system is constructed in which the output of the subtracter 36 is zero.

The tracking error signal 24 is input to the drive circuit 46 via the phase compensation circuit 49, switch 48, and switch 41,
Tracking servo is performed by supplying a drive current to the tracking drive coil 12 of the actuator IO to drive the objective lens 5 in the radial direction of the optical disc 7.

Next, the slider motor 1 during the rough search of the optical head 13
4. A method of controlling the tracking drive coil 12 will be explained.

When the coarse search command 45 is output from the system control circuit 26, the switch 39 and the switch 41 are connected to the b side. As a result, the slider servo loop is turned off, and the output signal 43 of the slider voltage generation circuit 42 is input to the drive circuit 47. Although not shown here, the slider voltage generation circuit 42 outputs a trapezoidal wave signal, for example, while comparing the number of tracks up to the target address on the disk with the actual number of track crossings obtained from the tracking error signal 24. The slider motor 14 is rotated by the drive current of the drive circuit 47, and the optical head 13 is moved to the vicinity of the target address on the disk.

Also, at this time, the tracking servo loop is switched to switch 4.
1 turns it off. As a result, instead of the tracking error signal 24, a signal from the output of the subtracter 36 via the phase compensation circuit 37 is input to the drive circuit 46. The output of the subtracter 36 is a signal that becomes zero when the objective lens 5 suspended by the support means is in a free state, and by applying this to the tracking drive coil 12, the objective lens 5 is in a free state. As a result, it is possible to prevent the objective lens 5 from vibrating during a rough search.

[Effects of the Invention] According to the present invention, when the optical disc device starts operating, the value of the objective lens position signal at the time when the focus servo is turned on is stored, and tracking control and slider control are performed using this as a reference signal. In addition, even if the position of the objective lens changes over time, the position signal of the objective lens in a free state at the start of operation is stored and used as a reference signal as soon as it occurs, so it is not affected by the adverse effects of the change over time. There is an advantage that there is no

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a timing chart of signals in the main part of FIG. 1, and FIG.
The figure is a plan view showing details of the optical head, and FIG. 4 is a diagram illustrating the operating principle of the photodetector. Explanation of symbols 9...Photodetector, 13...Optical head, 14...Slider motor, 33...Latch circuit agent Patent attorney Akio Namiki Figure 2

Claims (1)

[Scope of Claims] 1. A laser light source, an objective lens for focusing laser light emitted by the laser light source onto an optical disk, a photodetector for detecting the laser light reflected from the optical disk, and the objective lens. an actuator that movably suspends the lens in its optical axis direction and in the radial direction of the optical disk and can drive the lens in those directions, respectively; an optical disk with respect to the optical head of the objective lens obtained from the position detecting means, comprising at least: a position detecting means for detecting a relative position; and an optical head moving means for moving the optical head along the radial direction of the optical disk. A position signal representing a relative position along the radial direction is compared with a reference signal, and the deviation signal obtained as a result is used to control coarse movement of the optical head by the optical head moving means during optical disk reproduction, and also to control the deviation signal. In an optical disc device that controls the position of an objective lens relative to an optical head along a radial direction of an optical disc during a rough search for a desired track on an optical disc, when the optical disc device starts operating, the objective lens is free in the radial direction of the optical disc. A position signal representing a relative position of the lens with respect to the optical head along the radial direction of the optical disk in a state (a state in which the lens is freely suspended by the actuator without receiving any external force) is input from the position detection means. An optical disc device comprising a latch means for latching, and a position signal latched by the latch means is used as the reference signal.