JPS61287039A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To attain the locking of focus servo with high accuracy by moving an objective lens in the focusing direction while the lens is vibrated minutely in the focusing direction or in the tracking direction. CONSTITUTION:An output of an adder 3 is a superimposition between a minute DC voltage and a minute AC voltage by an AC signal oscillator 1 and a bias signal generator 2 at focus servo locking state and a focus magnetic circuit 6 is driven by a current proportional to the voltages. The objective lens is driven while the friction between a moving member and a bearing transits from the static friction into the kinematic friction, and when the output of the bias signal generator 2 starts increasing, the objective lens is moved smoothly accordingly in the focus direction while being fluctuated minutely. Thus, a focus state detection circuit 7 discriminates the focus servo locking direction, changes over an output signal of a changeover circuit 4 from the output of the adder 3 into an output of an amplifier 8 to lock the focus servo.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention irradiates a light beam onto an optical information recording surface through an objective lens, and receives the light beam from the disk through the objective lens and returned by a light receiving section. The present invention relates to an optical information recording and reproducing device that records and reproduces information in this manner.

Conventional technology When moving the objective lens in the focus direction and pulling in the focus servo, the focus magnetic circuit is driven by a monotonically increasing current, the objective lens is gradually brought closer to the information recording surface, and the focus servo circuit is closed at just the focus point. Therefore, focus servo was performed.

Problems to be Solved by the Invention In such conventional devices, the friction between the support shaft and the movable member that holds the objective lens, which is slidably supported with respect to the support shaft, is different between when it is stationary and when it is in operation. Because of the difference, the objective lens did not move smoothly toward the information recording surface when the focus servo was pulled in, causing problems such as stick-slip and the objective lens colliding with the information recording medium such as a disk. .

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides objective lens excitation movement in which the objective lens is moved in the focus direction while being slightly vibrated in the focus operation direction and/or tracking operation direction when the focus servo is pulled in. It is driven by means.

Function The present invention uses the objective lens excitation and movement means to cause a movable member that holds the objective lens, which is slidably supported with respect to the support shaft, to be in an operating state by slightly vibrating it with respect to the support shaft, and in this state, to focus. By moving it in the operating direction, the objective lens moves smoothly and the focus servo pulls in with precision.

Embodiment FIG. 1 is a block diagram showing an embodiment of the optical information recording/reproducing apparatus of the present invention. In FIG. 1, 1 is an AC signal oscillator that generates an AC voltage with minute amplitude, 2 is a bias signal generator that generates a voltage that increases monotonically and slowly, and 3
4 is an adder that has input terminals 14 and 16 and outputs the added value to terminal 16; 4 has input terminals 11 and 12; and input terminal 11 is input by a signal from switching signal input terminal 10.
and 12, a switching circuit that outputs either signal to the output terminal 13; 6, a drive circuit that causes a current proportional to the output voltage of the switching circuit 4 to flow through the focusing magnetic circuit 6; 7;
8 is a focus state detector; 8 is an amplifier for amplifying the output of the focus state detector; 9 determines the focus servo pull-in range from the output of the focus state detector and outputs a switching signal to a terminal 1o of the switching circuit 4;

FIGS. 5 and 6 are oblique and sectional views of the objective lens driving section. 22 is an objective lens, which is held by the movable member 120. 21 is a first yoke and a movable member 20
It is a support shaft that supports the. The focus operation direction is driven by a seven-occasion magnetic circuit composed of a focus coil 23 and a first magnet 26. The tracking operation direction is driven by a tracking magnetic circuit composed of a tracking coil 24 and a second magnet 28 .

During focus servo pull-in, a voltage shown in FIG. 2 is output to the AC signal oscillator 1, and a voltage shown in FIG. 3 is output to the bias signal generator 2. It has a minute DC voltage that moves the objective lens minutely from 0 to 11 hours. The output of the adder 3 is as shown in FIG. The switching circuit 4 initially outputs the input from the input terminal 12, and the focusing magnetic circuit 6 is driven with a current proportional to the voltage shown in FIG. 0
6, the objective lens 22 in FIG. 6 changes from the static friction state between the movable member 20 and the bearing portion 20a to the dynamic friction state,
, and start working. At time t, the output of the bias signal generator 2 begins to increase, and correspondingly, the objective lens moves smoothly in the focus direction while fluctuating minutely. The focus state detection circuit 7 determines the focus servo pull-in range and switches the output signal of the switching circuit 4 from the output of the adder 3 to the output of the amplifier 8. The output of the amplifier 8 is a signal that is proportional to the output of the focus state detection circuit 7 and acts in the direction of negative feedback, so that the focus servo is pulled in. In this embodiment, a slight vibration is made in the focus operation direction, but it is clear that the same operation can be performed even if a minute vibration is made in the tracking operation direction.

Effects of the Invention As described above, according to the present invention, the focus servo can be pulled in stably and accurately without stick-slip, and is extremely useful in practice.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an optical information recording device according to an embodiment of the present invention, Fig. 2 is an output waveform diagram of an AC voltage oscillator of the same device, and Fig. 3 is an output of a monotonically increasing voltage generator of the same device. Waveform diagram, Figure 4 is the output waveform diagram of the adder of the same device, Figure 6
The figure is a perspective view of the objective lens drive section of the same apparatus, and FIG. 6 is a sectional view of the objective lens drive section of the same apparatus. 1... AC signal oscillator, 2... Bias signal generator, 2o... Movable member, 20a...
... Bearing part, 22 ... Objective lens. Name of agent: Patent attorney Toshio Nakao and 1 other person1-
-Ichitsuta Tsuchienenne Z-11 Bias Shinpokujima 3-11 Karo Sanmei (4--All Susou Search Circuit, 3--Ichitan Bando)

Claims (2)

[Claims] (1) A support shaft, a movable member slidably supported on the support shaft, an objective lens held at a position eccentric to the axis of the support shaft of the movable member, and A focusing magnetic circuit for driving the objective lens in the focusing direction, a tracking magnetic circuit for driving the objective lens in the tracking direction, and a tracking magnetic circuit for driving the objective lens in the focusing direction and/or the tracking operation direction when the focus servo is pulled in. objective lens excitation and movement means for moving the objective lens in the focus direction while causing minute vibrations;
An optical information recording/reproducing device comprising: a focus state detection means for detecting a focus state; and a focus direction drive signal switching means for detecting a focus servo pull-in position and pulling the focus direction into a control state. (2) a minute alternating current signal oscillator that generates an alternating current signal that minutely drives the objective lens in the focusing operation direction and/or tracking operation direction, and a bias signal generator that generates a monotonically increasing and/or direct current signal; Claims include an objective lens excitation and movement means comprising an adder that adds the output of the minute AC signal oscillator and the output of the bias signal generator, and a drive circuit that drives the objective lens in proportion to the output of the adder. 2. The optical information recording and reproducing device according to item 1.