JPH04181571A - Pick-up drive device - Google Patents

Abstract

PURPOSE:To enable a motor to be driven positively when a tracking error signal exceeds a specified level and at the same time prevent overrun by separating a starting circuit of the motor from a stopping circuit. CONSTITUTION:A tracking error signal from an input terminal 1 which is amplified by an amplification circuit 2 is integrated by an integration circuit 5 and is supplied to-input terminal a of an amplification circuit 4 with a hysteresis characteristic. When the signal which is supplied to the terminal a exceeds a specified level, an output signal is generated abruptly, thus enabling a motor for driving pick-up 6 to be rotated. When the tracking error signal reaches 0, an output signal of the circuit 4 becomes 0, thus enabling the motor 6 to be stopped. At this time, when an optical pick-up exceeds extremely, a tracking signal in inverse polarity is detected and a negative signal is applied to the terminal a of the circuit 4. Therefore, the motor 6 can be driven and the entire optical pick-up can be moved in inverse direction, thus enabling the motor to be driven positively and preventing overrun.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a drive device for an optical pickup used for an optical disc such as a CD player.

(b) Conventional technology In an optical disc player such as a CD player, a light beam is emitted from an optical pickup, irradiated onto the tracks of the disc, and the signals recorded on the disc are extracted and reproduced. If a deviation occurs because the beam is not irradiated to the center of the track, a photodetector detects this and generates a tracking error signal. The tracking error signal is, for example,
As described in Publication No. 0907, when the deviation of the light beam from the track is small and the tracking signal is small, in addition to the tracking coil, the objective lens of the optical pickup is moved so that the light beam is correctly irradiated onto the track. However, as reproduction progresses, simply moving the objective lens will not correctly irradiate the track with the light beam, making tracking impossible. In such a case, the motor is rotated to drive the entire pickup so that the light beam is correctly irradiated onto the truck.

(c) Problems to be Solved by the Invention As mentioned above, tracking is achieved by adding a tracking error signal to a tracking coil during a short period of time, and driving a motor when the tracking signal exceeds a predetermined level. The tracking error signal is smoothed by an integrating circuit in order to eliminate the eccentricity component of the disk and make it a signal due only to the deviation from the track. However, if the constant of the integrating circuit is made large, the motor stops and the pickup goes too far from the center of the truck.If the constant of the integrating circuit is made small, especially if the motor is made small, cogging will be large and the torque constant will be small. The starting voltage was high and the variation was also large.

In order to eliminate such drawbacks, the present invention separates the motor starting circuit and the stop command circuit, thereby ensuring that the motor is reliably activated when the light beam deviates from the track by a predetermined amount or more and the tracking error signal exceeds a predetermined level. Along with driving the
To provide an optical pickup driving device which prevents excessive overshoot as much as possible, does not apply voltage to the motor until starting is reached, and reduces wasteful current to the motor.

<2) Means for Solving the Problems The optical pickup driving device of the present invention includes a first amplifier circuit for amplifying a detected tracking error signal, a tracking coil connected to the first amplifier circuit, and one terminal connected to the A second amplifier circuit is connected to the first amplifier circuit through an integrating circuit, and the other terminal is directly connected to the first amplifier circuit and has a hysteresis characteristic, and the second amplifier circuit is driven by the output signal of the second amplifier circuit. It is composed of a pickup drive motor.

(*) Function Since the optical pickup driving device of the present invention has the above-described configuration, the optical pickup is amplified by the first amplifier circuit, and the second
When the tracking error signal supplied to one terminal of the amplifier circuit reaches a predetermined level, the second amplifier circuit generates an output signal, rotates the drive motor, moves the pickup body, and corrects the tracking deviation. The displacement of the tracking coil can be corrected by detecting that the tracking signal from the first amplifier circuit has fallen below a certain level, stopping the output signal from the second amplifier circuit, and stopping the rotation of the pickup motor.

(f) Embodiment An embodiment of the optical pickup driving device of the present invention will be described with reference to the drawings.

In FIG. 1, 1 is an input terminal to which a tracking error signal detected by a photodetector (not shown) is applied.

2 is a first amplification circuit that amplifies the tracking signal; 3
is a tracking coil to which the tracking error signal amplified by the first amplifier circuit 2 is applied, and moves the objective lens to correct tracking deviation. Reference numeral 4 denotes a second amplifier circuit, one input terminal a of which is connected to the output terminal of the first amplifier circuit 2 via an integrating circuit 5, and the other input terminals are directly connected to the first amplifier circuit 2.

As shown in FIG. 2, the second amplifier circuit 4 has a hysteresis characteristic in the positive direction and a gain characteristic in the negative direction similar to a normal amplifier. Therefore, the tracking error signal from the amplifier circuit 2 is integrated by the integrating circuit 5, and no output signal is generated until the input signal Vin applied to one input terminal a reaches a predetermined level A. Output signal V. and said output signal V. Once this occurs, tracking is achieved, the tracking error signal from the first amplifier circuit 2 becomes zero, and an output signal is generated until the signal applied to the other input terminal reaches zero level.
The signal applied to the other input terminal is reset to zero level, and the output signal of the second amplifier circuit 4 becomes zero. 6 is a pickup driving motor that slides the optical pickup main body (not shown).

Next, the operation of the optical pickup driving device of the present invention will be explained.

For example, when a CD disc is being played back, a light beam emitted from an optical pickup is irradiated onto a track formed on the surface of the CD disc, and the light beam is irradiated onto a track formed on the surface of the CD disc. to reflect the light beam. The reflected light beam is detected by a photodetector (not shown), and the information signal is extracted and reproduced.

Incidentally, as the reproduction progresses, it is necessary that the light beam be correctly irradiated to the center of the spiral track. Therefore, a tracking error is detected from the signal applied to the photodetector, and a tracking error signal is generated. The tracking error signal is supplied from the input terminal 1 to the first amplifier circuit 2 and amplified, and the amplified tracking error signal is supplied to the tracking coil 3.

As a result, magnetic flux is generated from the tracking coil 3, and tracking is performed by moving the objective lens (not shown) so that the light beam correctly irradiates the track.In this way, as the reproduction progresses, the tracking coil 3 tracks the track. Tracking is performed by supplying an error signal and moving the objective lens so that the light beam always irradiates the center of the track. However, as playback progresses, it becomes impossible to track simply by moving the objective lens, so in that case, the pickup drive motor is moved and the entire optical pickup is slid across the track, so that the objective lens is at the center of the track. It needs to be positioned above. Therefore, in the present invention, the tracking error signal amplified by the first amplifier circuit 2 is integrated by the integrating circuit 5, and is supplied to one input terminal a of the second amplifier circuit 4, so that the signal supplied to the one input terminal a is When the level exceeds a predetermined level, an output signal is suddenly generated to rotate the pickup drive motor 6. When the pickup drive motor 6 is rotated, the entire optical pickup is moved across the track, and the objective lens is positioned at the center of the track. When the objective lens is positioned directly above the track, there is no deviation of the light beam irradiating the track, and the tracking error signal becomes zero. As a result, the other input terminals of the second amplifier circuit 4 go to zero level, so a reset occurs and the output signal of the second amplifier circuit 4 becomes zero, stopping the pickup drive motor 6 and applying the tracking signal to the tracking coil 3 again. , tracking is performed by moving the objective lens.

In the above, when the other input terminal b of the second amplifier circuit 4 reaches zero level, the output signal of the second amplifier circuit 4 is reset to zero and the pickup drive motor 6 is stopped, but the optical pickup still does not work. When it goes too far, the photodetector detects a tracking error signal with the opposite polarity, so the tracking error signal with the opposite polarity is amplified by the first amplifier circuit 2 and then sent to one of the second amplifier circuits 4. It is applied to input terminal a as a negative signal in the opposite direction to the above. In response to this negative signal, the second amplifier circuit 4 operates as a normal amplifier, so it generates an output signal in response to the tracking error signal, drives the pickup drive motor 6, and moves the entire optical pickup in the opposite direction. Move to compensate for excess.

In the above, when the signal supplied to the other input terminal of the second amplifier circuit 4 becomes zero level, the output signal of the second amplifier circuit 4 is set to zero level, but the signal level of the other input terminal The output signal may be set to zero when the level becomes negative, or the output signal may be set to zero level after a certain period of time after the output signal is generated from the second amplifier circuit 4.

(g) Effects of the Invention As described above, the optical pickup driving device of the present invention has a hysteresis characteristic in the amplifier circuit that supplies the driving voltage to the pickup driving motor, and is based on the tracking error signal supplied to one input terminal. Since the output signal is not generated until the signal reaches a predetermined level, unnecessary voltage consumption is eliminated, and there is no tracking error signal. Since the output signal of the amplifier circuit disappears after a certain period of time, it is possible to prevent the entire optical pickup from overshooting.If the optical pickup goes too far, the amplifier circuit generates an output signal according to the distance traveled, and the optical pickup circuit generates an output signal according to the distance traveled. Since the pickup is moved in the opposite direction, tracking deviation can be reliably corrected.

[Brief explanation of the drawing]

FIG. 1 is a diagram of an optical pickup drive circuit of the present invention, and FIG. 2 is a characteristic diagram of an amplifier circuit used in the optical pickup drive circuit of the present invention. 2... First amplifier circuit, 3... Tracking coil, 4... Second amplifier circuit, 6... Optical pickup driving motor.

Claims (3)

[Claims] (1) a first amplifier circuit that amplifies a detected tracking error signal; a tracking coil connected to the first amplifier circuit; and one input terminal connected to the first amplifier circuit via an integrating circuit; A second amplifier circuit whose other input terminal is directly connected to the first amplifier circuit and has a hysteresis characteristic, and a pickup drive motor driven by the output signal of the second amplifier circuit, which is amplified by the first amplifier circuit. When the tracking error signal supplied to one input terminal of the second amplifier circuit via the integrating circuit reaches a predetermined level, an output signal is generated from the second amplifier circuit, and the tracking signal from the first amplifier circuit remains constant. A pickup driving device characterized in that the output signal from the second amplifier circuit is stopped upon detecting that the voltage has dropped below the level, and the rotation of the pickup driving motor is stopped. (2) A first amplifier circuit that amplifies the detected tracking error signal, a tracking coil connected to the first amplifier circuit, and an input terminal connected to the first amplifier circuit via an integrating circuit to achieve hysteresis characteristics. and a pickup drive motor driven by the output signal of the second amplifier circuit, the pickup drive motor being amplified by the first amplifier circuit and supplied to the input terminal of the second amplifier circuit via an integrating circuit. When the tracking error signal reaches a predetermined level, the second amplifier circuit generates an output signal, and when a predetermined time elapses, the output signal from the second amplifier circuit is stopped, and the rotation of the pickup driving motor is stopped. An optical pickup drive circuit characterized by: (3) a first amplifier circuit that amplifies the detected tracking error signal; a tracking coil connected to the first amplifier circuit; one terminal connected to the first amplifier circuit via an integrating circuit; a second amplifier circuit whose terminal is directly connected to the first amplifier circuit and has hysteresis characteristics in the forward direction and normal amplification characteristics in the reverse direction; and a pickup drive driven by the output signal of the second amplifier circuit. and an output signal from the second amplifier circuit when the tracking error signal amplified by the first amplifier circuit and supplied to one terminal of the second amplifier circuit via the integrating circuit reaches a predetermined level. , detects that the tracking signal from the first amplifier circuit has become zero, stops the output signal from the second amplifier circuit, stops the rotation of the pickup motor, and prevents the optical pickup from overshooting, causing a tracking error with the opposite polarity. When the signal is generated, the optical pickup drive circuit generates a signal corresponding to the overshoot distance of the optical pickup from a second amplifier circuit, and reversely rotates the optical pickup drive motor to correct the overshoot of the optical pickup. .