JPS6148134A - Optical disc device - Google Patents

Abstract

PURPOSE:To focus an objective lens on a recording layer stably and accurately by shaking radially the objective lens at focus servo locking and closing a servo loop when a trach error signal reaches a value. CONSTITUTION:In a focus servo locking operation, when a focus servo locking operation control signal 11 is fed at a point of time T1 of focus servo locking start, a flip-flop 10 is set and a loop changeover switch 3 is changed over to the position of an initialize signal generating circuit 7 to start the locking operation. Then the circuit 7 generates a signal B and a tracking initialize signal generating circuit 8 generates a signal A at the same time. The signals are fed to an actuator driving the objective lens via servo amplifiers 4,6 to move the lens 31 while being shaken in the radial direction F toward G and the lens approaches a medium 32. Thus, an optical disc device having a focus servo focused to the recording layer stably and accurately is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an optical disc device, and more particularly to an optical disc device having a focus taper control circuit.

(Prior art) Conventionally, in this type of optical disk device, when pulling in the focus servo, in order to perform stable pulling in the linear part of the 7-occasion error signal, the lens is gradually brought closer to the medium, and the focus error signal is brought into the linear part. Focus servo pull-in was performed when the level increased to a level K at which it was possible to judge from the total reflection signal that the focus servo was applied. However, in such an optical disk device, when the reflectance of the medium changes or varies.

Furthermore, when the detection level of the total reflection signal fluctuates due to temperature changes, etc., the expected stable focus servo pull-in cannot be achieved, and the focus is on the surface of the cover glass instead of the recording layer of the medium.

(Object of the Invention) An object of the present invention is to provide an optical disc device that eliminates the drawbacks of conventional optical disc devices and that can stably and reliably focus on the recording layer of the medium.

(Structure of the Invention) According to the present invention, an optical disc device for recording and reproducing information on an optical disc medium includes a circuit for swinging an objective lens in a radial direction with respect to the medium when a focus servo is pulled in, and a tracking error signal. There is obtained an optical disc device characterized in that it has a circuit for determining whether a tracking error signal has reached a certain level, and a control circuit that closes a focus servo loop when a tracking error signal reaches a certain level.

(Function) As a means of detecting the linear part of the focus error signal, the present invention actively detects the track error signal obtained only when focusing near the recording layer by swinging the lens in the radial direction when gradually bringing the lens closer to the medium. This is an optical disc device that detects this level and performs focus servo pull-in.

(Example) Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the invention. In FIG. 1, one embodiment of the present invention is an optical disk device that records or reproduces information on an optical disk medium, and includes an optical head 1 provided facing the medium, and an objective of the optical head 1 that is placed facing the medium when the focus servo is pulled in. A circuit 213.4 for swinging the lens in the radial direction, a circuit 5.9 for determining when the track error signal has reached a certain level, and a control for closing the focus servo loop when the track error signal reaches a certain level. a circuit 1O, a tracking chibore/pro for tracking control of the optical head 1, and an initialization signal generator 7.8 that operates when the focus servo is pulled in and supplies control signals to the focus servo amplifier 4 and the tracking servo 6. including.

The optical head 1 includes a photodetector and an actuator (not shown) for applying focus servo and tracking servo, respectively. The focus servo is composed of the optical head 1, a focus error detector 2 connected to the optical head L and detecting focus air, a loop changeover switch 3, a focus servo amplifier 4, and a loop formed by K. There is. The loop changeover switch 3 is connected to the initialization signal generator 7 during the focus servo pull-in operation. The initialization signal generator 8 is a signal generator that supplies the tracking actuator to the optical head 1K via the tracking chibo/pro.
I'm lil. Since the tracking circus loop is not directly related to this case, it is not shown and its explanation will be omitted.

The focus pull-in operation control signal 11 is generated by the initialization signal generator 7. 8 and is connected to the slip 70 knob IOK that controls the loop selector switch 3.

The flip-flop 10 is connected to be reset by the output signal of a comparator 9 which detects that the output signal of the tracking error detector 5, which is connected to the optical head IKR, has reached a certain level.

In the focus servo pull-in operation, when the focus servo pull-in operation control signal 11 is supplied at the focus servo pull-in operation start point T1, the 7 lip 70 knob 10 is set, and the loop changeover switch 3 is turned to the initialization signal generation circuit 7 side. 7 at the same time that it is started
The tracking initialize signal generating circuit 7 generates the signal B shown in FIG. 2, and the tracking initialize signal generating circuit 8 generates the signal A. These signals are servo amplifier 4.6
is applied to the actuator that drives the objective lens through the lens 31 in the radial direction PK as shown in FIG.
It moves in the G direction without swinging and approaches the medium 32.

The signals that appear in this process are a focus error signal C1) a racking error signal, and a total reflection signal E, as shown in FIG. In the conventional technology, it was determined that the focus error signal C was applied to a linear part by detecting the level of the total reflection signal E at that part. If the detection level reference voltage fluctuated due to temperature, etc., the focus servo could not be retracted properly, which caused the camera to focus on the surface of the Shikapera glass. This possibility becomes particularly high when the cover glass and the recording layer are close to each other.

Incidentally, Vc7 orcus error signal signal C is an error signal caused by reflection on the surface of the glass. In the focus servo pull-in according to this embodiment, when the comparator 9 detects that the track error signal that appears only in the recording layer has been compared to a certain degree, the 7 lip-flop lO is reset, and the loop changeover switch 3 is used to set the focus servo pull-in point T2. , close the focus servo loop. By doing this, in this embodiment, it is possible to realize an optical disc device having a focus servo that stably and accurately focuses on the recording layer.

(Effects of the Invention) As explained above, the present invention swings the objective lens in the radial direction during the 1c7 orcus servo pull-in operation and closes the servo loop when the track error signal reaches a certain value, thereby stably and accurately recording. It has the effect of focusing on layers.

[Brief explanation of drawings]

FIG. 1 is a block diagram partially showing an embodiment of the present invention, FIG. 2 is a diagram showing each signal in an embodiment of the present invention,
FIG. 3 is a diagram showing the relationship between a medium and a lens in an embodiment of the present invention. l...Optical head, 2...7 Occurrence error signal detector, 3...Loop changeover switch, 4...Focus servo amplifier, 5...・・・
... Tracking error detection circuit, 6 ... Tracking servo amplifier, 7 ... Focus initialization signal generator, 8 ... Tracking initialization signal generator, 9 ... ... Comparator, 1
0...Flip 70 cups, 11...Focus servo pull-in control signal, 31...Objective lenses 1, 32...Medium, A...・Focus initialization signal, B...Tracking initialization signal, C...Focus error signal, D...Track error signal, E...
... Total reflection signal, C' ... Focus error signal generated on the surface of the cover glass, Tl ... Focus servo pull-in operation start point, ￥2 diagram

Claims (1)

[Claims] In an optical disk device that records and reproduces information on an optical disk medium, a circuit that swings the objective lens of an optical head in the radial direction relative to the medium when the focus servo is pulled in, and a circuit that determines when a track error signal has reached a certain level. and a control circuit that closes a focus servo loop when a track error signal reaches a certain level.