JPH01176331A - Optical axis aligning device for optical pick-up - Google Patents

Abstract

PURPOSE:To stabilize a track following servo by controlling the position of a slider with an analog signal from a low-pass filter to remove the high area component of the analog signal, which shows the target position of the slider corresponding to the address of a target track, and the analog signal to show the present position of the slider. CONSTITUTION:A low-pass filter 8 is provided to remove the high area component of the analog signal, which shows the target position of a slider 7 corresponding to the address of the target track, and the position of the slider 7 is controlled by the analog signal from this low-pass filter 8 and the analog signal showing the present position of the slider 7. Accordingly, since the analog signal showing the target position of the slider 7, which corresponds to the address of the target track, goes to a smooth signal, large force is not added to an objective lens instantaneously when the slider 7 is moved. Thus, the stable track following servo can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical axis alignment device for an optical pickup used in an optical disk device or the like.

2. Description of the Related Art In general, optical disk devices and the like include a semiconductor laser that outputs a beam, an objective lens that focuses the beam and irradiates it onto a recording medium such as an optical disk, and an objective lens that collects the reflected light of the beam from the recording medium. It has an optical pickup equipped with an element that receives light through the optical pickup.

The optical pickup is movable by a slider in the radial direction of the recording medium so that the beam tracks and coarsely seeks the trunk of the recording medium.

FIG. 2 shows an optical axis alignment device for an optical pickup in a conventional optical disk device.

In FIG. 2, the ternarization circuit 1 determines whether or not the optical axis of the objective lens of the optical pickup is deviated from the center of its movable range based on the output of a position detection sensor (not shown), and if so, the direction thereof. Detects the central processing unit (CPU
)2, when the ternarization circuit 1 detects a deviation of the optical axis, it increases or decreases the least significant bit LSB of the address of the target track by "1" depending on the direction, and converts the target value of the slider to a digital value. Output as a signal.

When the digital target value from the CPU 2 is converted into analog by the D/A converter 3, the subtracter 3a outputs the difference between this target value and the current value (current position output of the detector of the slider 7) as a slider error signal. .

The phase of this slider error signal is compensated by a phase compensation circuit 4, this slider error signal is amplified by a voltage amplification circuit 5, and a slider drive circuit 6 drives a slider 7 according to the slider error signal from the voltage amplification circuit 5. and align the optical axis of the objective lens of the optical pickup.

That is, the phase compensation circuit 4, voltage amplification circuit 6, slider drive circuit 6, and slider 7 constitute a track following-servo loop of this optical axis alignment device.

Problems to be Solved by the Invention However, in the above-mentioned conventional optical axis alignment device for an optical pickup, since the CPtJ2 outputs the target value for moving the slider as a discrete value, when the slider 7 moves, A large force is instantaneously applied to the objective lens, which causes a large disturbance to the tracking servo.
There is a problem in that an abnormality occurs in the track following servo.

SUMMARY OF THE INVENTION In view of the problems of the prior art described above, it is an object of the present invention to provide an optical axis alignment device for an optical pickup that can perform stable track following servo.

Means for Solving the Problems In order to solve the above problems, the present invention provides a low-pass filter that removes high-frequency components of an analog signal indicating the target position of the slider corresponding to the address of the target track. The position of the slider is controlled by an analog signal from a pass filter and an analog signal indicating the current position of the slider.

Effect of the Invention With the above configuration, the analog signal indicating the target position of the slider corresponding to the address of the target track becomes a smooth signal. Therefore, when the slider moves, a large force is not instantaneously applied to the objective lens, resulting in a stable signal. Track following servo can be performed.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of an optical axis alignment device for optical pink-up according to the present invention, and the same constituent members as those shown in FIG. 2 are given the same reference numerals.

In FIG. 1, 1 detects whether the optical axis of the objective lens of the optical pick-up is deviated from the center of its movable range and, if deviated, the direction thereof, by the output of a position detection sensor (not shown). The ternarization circuit 2 increases or decreases the least significant bit LSB of the address of the target track, which is the target value of the slider, by "1" according to the direction of the optical axis deviation detected by the ternarization circuit. A central processing unit (CPU) 3 that updates the target address is a D/A converter that converts the digital value corresponding to the target address from the CPU 2 into an analog converter.

8 is a low-pass filter (LPF) that removes high-frequency components of the target value signal from the D/A converter 3; 3a is a filter that removes the target value from the low-pass filter 8 and the current value (the current position of the detector of the slider 7); This is a subtracter that outputs the difference between the two outputs as a slider error signal.

4 is a circuit for compensating the phase of the slider error signal from the subtracter 3a; 6 is a circuit for voltage amplifying the slider error signal from the phase compensation circuit 4; and 6 is a circuit for voltage amplifying the slider error signal from the voltage amplification circuit 5. This is a slider driving circuit for driving the slider 7 to align the optical axis of the objective lens of the optical pickup.The slider 7 has a detector that detects the current position of the slider, and the detection signal is sent to the subtracter 3a.
Output to.

These phase compensation circuit 4, voltage amplification circuit 5, slider drive circuit 6, and slider 7 constitute a track following servo loop of this optical axis alignment device.

Next, the operation of the embodiment according to the above configuration will be explained.

In FIG. 1, when the ternarization circuit 1 detects that the optical axis of the objective lens of the optical pickup is shifted from the center of its movable range based on the output of a position detection sensor (not shown), the central processing unit ( The CPU) 2 updates the address of the target track according to the direction of the optical axis deviation, and updates the address of the target track according to the direction of the optical axis deviation, and
Directly outputs the target value digitally.

When the digital target value from the CPU 2 is converted into an analog signal by the D/A converter 3, this target value is a quantized level signal, and this signal is converted into a continuous smooth analog signal by the low-pass filter 8. .

Next, when the subtracter 3a outputs a slider error signal based on the difference between this smooth analog signal and the current value, the phase of this slider error signal is compensated by the phase compensation circuit 4, and this slider error signal is output by the voltage amplifier circuit 6. The slider drive circuit e drives the slider T according to the slider error signal from the voltage amplification circuit 6 to align the optical axis of the objective lens of the optical pickup.

Therefore, according to the above embodiment, since the target value signal input to the subtracter 3a is a continuous and smooth analog signal, the slider 7 moves smoothly, and therefore stable track following servo can be performed. .

DETAILED DESCRIPTION OF THE INVENTION As described in detail, the present invention includes a low-pass filter that removes high-frequency components of an analog signal indicating a target position of a slider corresponding to an address of a target track; Since the slider position is controlled by an analog signal indicating the current position of the slider, the analog signal indicating the target position of the slider corresponding to the address of the target track becomes a smooth signal. Stable trunk tracking servo can be performed without applying a large force to the lens instantly.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an optical axis alignment device for an optical pickup according to the present invention, and FIG. 2 is a block diagram showing a conventional optical axis alignment device for an optical pickup. 1... Ternary circuit, 2... Central processing unit (CPU)
, 3゛D/A converter/verter, 3a-subtractor, 4゛°/phase compensation circuit, 6...voltage amplifier circuit, 6...slider drive circuit, 7...slider, 8...row pass filter.

Claims (1)

[Claims] means for detecting whether or not the optical axis of an objective lens of an optical pickup is deviated from the center of its movable range, and if so, the direction thereof, and the direction when the detection means detects the deviation of the optical axis; means for changing the address of a target track according to the address of the target track and outputting it as a digital signal; means for converting the digital signal into an analog signal; a low-pass filter for removing high-frequency components from the analog signal; An optical axis alignment device for an optical pickup, comprising means for controlling the position of a slider using an analog signal from an analog signal indicating the current position of the slider.