JPS59193545A - Compact disk player - Google Patents

Abstract

PURPOSE:To increase the resistance to large vibration without increasing the amplification degree of a servo amplifier and also to suppress the generation of noise when the vibration is small, by detecting the actual vibration by a vibration pickup and adding them to a servo circuit. CONSTITUTION:When vibration is applied from the outside, a vibration pickup 16 detects the actual vibration. These vibration is amplified by an amplifier 17 together with conversion of impedance, and the high-frequency component is deleted by an LPF18. The output signal sent from the LPF18 is added to the focus error signal and the tracking error signal by adders 19 and 20, respectively. The error signals are added to the inputs of adders 19 and 20 to obtain a larger output. This output is negatively fed back to an optical pickup 3 to drive an actuator 7. Thus the error signals are reduced. In other words, the servo error can be reduced by adding the detection signal to a servo circuit through the pickup 16 despite application of the same vibration.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a compact disc player, and particularly to a compact disc player including a vibration pickup for detecting external vibration and an adder for adding the detection signal to a servo circuit.
This relates to disc players.

FIG. 1 is a schematic block diagram showing an example of a servo circuit for controlling focus and tracking of a laser beam in a conventional compact disc player.

First, the servo circuit of a conventional compact disc player will be explained with reference to FIG.

In FIG. 1, a compact disc 1 is rotated by a disc motor 2, and an optical pickup 3 reads information on the disc surface of the compact disc 1 by irradiating a laser beam.

That is, the optical pickup 3 emits a laser beam from a light source 4 as shown in FIG. 1, and the laser beam whose direction is changed by a half mirror 5 is focused by an objective lens 6 and irradiated onto the disk surface. . Furthermore, an actuunitough is provided in association with the objective lens 6. This actuator 7 drives the objective lens 6 vertically or horizontally when viewed from the surface of the disk 2, and moves the condensing position of the laser beam. The laser beam reflected by the disk 2 is incident on a light detector 9 via an objective lens 6, a half mirror 5, and a cylinder lens 8. The output from the optical detector 9 includes an information signal read from the disk surface, a focus error signal indicating whether the laser beam is accurately focused on the disk surface, and a focus error signal that correctly traces the information track on the disk surface. Contains a tracking error signal that indicates whether the

Since each of these signals has a unique frequency band, a focus error signal and a tracking error signal are extracted by filter circuits 10 and 11, respectively. These signals are amplified and impedance-converted by preamplifiers 12 and 13, respectively, and further power amplified by a focus error servo amplifier 14 and a tracking error servo amplifier 15, respectively. The outputs of the servo amplifiers 14 and 15 are output from the optical pickup 31\
A servo circuit is formed which operates to reduce focus errors and dragging errors by driving the actuator 7 with negative feedback and moving the objective lens in vertical and horizontal directions. therefore,
In order to improve the vibration resistance of focusing and tracking against external vibrations, it is sufficient to increase the amplification degree of each servo amplifier.

However, the laser beam applied to the optical pickup 3 may erroneously detect scratches or dirt on the disc surface as a focus error or tracking error, even if there is little or no external vibration. This results in unnecessary servo amplification, so increasing the amplification of the servo amplifier as shown in the example above had the disadvantage that noise caused by scratches and dirt would be produced even less.

Therefore, the main object of the present invention is to provide a compact disc player that overcomes the above-mentioned drawbacks and is resistant to vibration and stable.

In summary, this invention can be summarized as:
A compact disc player having a servo circuit which responds to an error signal representative of an error associated with vibration and controls to reduce said error, includes a vibration pickup that actually detects external vibrations, and a vibration pickup that actually detects external vibrations. By providing an adder that adds the detection output of the pickup to the servo circuit, a larger servo amplification output can be obtained without greatly increasing the amplification degree of the servo amplifier.

The above objects and other objects and features of the present invention will become more apparent from the detailed description given below with reference to the drawings.

FIG. 2 is a schematic block diagram showing one embodiment of the present invention. The example shown in FIG. 2 is similar to the first example described above except for the following points.
It is the same as the block diagram shown in the figure. That is, a vibration big amplifier 16 for detecting external vibration, an amplifier 17 for amplifying the output of the vibration pickup 16, and a low-pass filter 18 for removing high frequency components of the amplifier 17 are provided, as well as a servo amplifier 14 for focus error and a tracking error. Adders 19 and 20 for adding the output from the low-pass filter 18 are inserted in series before the servo amplifier 15, respectively.

FIG. 3 t3J and FIG. 4 are waveform diagrams for explaining the embodiment shown in FIG. 2.

Next, the operation of the embodiment shown in FIG. 2 will be explained with reference to FIGS. 3 and 4. When vibration is applied from the outside to the device shown in FIG. 2, the actual vibration is detected by the vibration pickup 16, amplified and impedance-converted by the amplifier 17, and high frequency components are removed by the low-pass filter 18. The output signal from the low-pass filter 18 is added to the focus error signal @ and the tracking error signal by an adder 19.20.

Suppose now that vibrations are being applied to the compact disc player. Let us now consider the case where there is no vibration pickup. Detected by optical pickup 3, adder 1
For example, the error signal input to 9 or 2o
If it is as shown in FIG. 3(1), the output of the adder is equal to the input as shown in FIG. 3(2).

Next, consider the case where there is a vibration pickup. When the input from the vibration pickup 16 to the adder 20 is as shown in FIG. 4 (1), the error signal (2) is added thereto to obtain a larger output as shown in FIG. 4 (3). Since this output is negatively fed back to the optical pickup 3 and drives the actuator 7, the error signal becomes small as shown in FIG. 4 (4). That is, even though the same vibration is applied, the servo error can be reduced by adding a detection signal to the servo circuit through the vibration pickup.

As described above, according to the present invention, by detecting actual vibrations using a vibration pickup and adding them to the servo circuit, vibration resistance against large vibrations is increased without increasing the amplification degree of the servo amplifier, and vibration resistance is increased. When the value is small, a stable compact disc player with less noise can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram showing an example of a servo circuit of a conventional compact disc player. FIG. 2 is a schematic block diagram of an embodiment of the present invention. 3 and 4 are waveform diagrams for explaining the operation of the embodiment shown in FIG. 2. In the figure, 1 is a compact disk, 2 is a disk motor, 3 is an optical pickup, 4 is a light source, 5 is a half mirror, 16 is an objective lens, 7 is an actuator, 8 is a cylinder lens, 9 is a light detector, 10. 11 is a filter circuit, 12.13 is a preamplifier, 14.15 is a servo amplifier, 16 is a vibration pickup, 17 is an amplifier, 18 is a low-pass filter, and 19.20 is an adder. Agent Masuo Oiwa Figure 1 7th

Claims (1)

[Scope of Claims] An optical pickup is provided for optically reading recorded information from a compact disc on which information is recorded, and the optical pickup detects an error signal representing an error occurring in connection with vibration; servo amplification means for controlling to reduce the error in response to the error signal from the optical pickup; external vibration detection means for detecting external vibration; and an adder for adding the vibration detection output to the error signal. A compact disc player, comprising: obtaining a larger servo amplification output by adding the error signal and the vibration detection output.