JP3037005B2 - Tilt servo device for optical disk player - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tilt servo device for an optical disk player for controlling the tilt of the optical pickup so that the optical pickup is oriented perpendicular to the disk.

[0002]

2. Description of the Related Art As an optical disk player for reading a signal recorded on a disk by a light beam using an optical pickup, a video disk player for reproducing a disk on which a video signal is recorded is known. In the video disc player, as is well known, a light beam emitted from an optical pickup in a radial direction of the disc in relation to reproduction of an analog video signal modulated by FM and reproduction of a large-diameter disc. Is provided perpendicularly to the disk surface, and a tilt mechanism for displacing the tilt of the optical pickup so that the light beam does not hit an adjacent track is provided, and a tilt servo device for controlling the tilt mechanism is provided. .

[0003]

As the tilt mechanism, a supporting mechanism for slidingly supporting the optical pickup in the radial direction of the disk and a driving mechanism for slidingly driving the optical pickup are displaced along the inclination of the disk surface. In general, a tilt sensor for detecting an inclination of a light beam of an optical pickup with respect to a disk by an optical reflection method is generally an optical sensor in which various optical components constituting the optical pickup are incorporated. Fixed to block base. In general, the tilt mechanism has a structure in which, when the tilt of the optical pickup is corrected along with the disc, the tilt amount of the optical pickup depends on the displacement amount of the tilt mechanism and even if the tilt mechanism has the same displacement amount. The distance between the tilt sensor and the disk changes due to the sliding displacement in the radial direction of the disk. Therefore, the amount of light emitted from the light emitting element of the tilt sensor, reflected by the disk, and received by the light receiving element of the tilt sensor changes according to the displacement of the tilt mechanism and the sliding displacement of the optical pickup,
This causes a problem that the accuracy of the detection sensitivity is not constant.

Further, as a tilt servo device, a tilt of a light beam of an optical pickup from a perpendicular to a disk obtained by using a sensor output from a tilt sensor in order to eliminate instability near a critical point of activation of a tilt mechanism. A dead zone is provided so that the tilt mechanism is not activated until the angle error output indicating the angle error reaches a predetermined value. If the amount of reflected light received by the light receiving element of the tilt sensor increases or decreases, the angle range of the dead zone changes. Therefore, a phenomenon occurs in which the tilt mechanism is started with a different value of the tilt angle error amount of the light beam of the optical pickup from the perpendicular to the disk due to the displacement amount of the tilt mechanism or the sliding displacement of the optical pickup. As the angle range of the dead zone increases, the leakage of the light beam from the optical pickup to the adjacent track increases, which causes a problem of deteriorating the reproduction signal.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and uses a sensor output from a tilt sensor to respond to an inclination angle of a light beam of an optical pickup from a perpendicular to a disk. An angle error output generation circuit for generating an angle error output, a hysteresis circuit for giving a hysteresis characteristic to the angle error output from the angle error output generation circuit, and reflection from a disk using a sensor output from the tilt sensor. A reflected light amount output generating circuit that generates a reflected light amount output according to the light amount, and drives a tilt mechanism according to the angle error output obtained through the hysteresis circuit, and obtains the reflected light amount output circuit. The amount of light emitted from the light emitting element of the tilt sensor is controlled according to the amount of reflected light output.

[0006]

The present invention relates to a tilt servo apparatus having a configuration in which the angle error output has a hysteresis characteristic to eliminate instability near a critical point for starting a tilt mechanism, and the amount of light emitted from the tilt sensor and reflected by the disk. Is detected using the sensor output from the tilt sensor,
By controlling the light emission amount of the light emitting element of the tilt sensor according to the detected reflected light amount, the displacement amount of the tilt mechanism,
Alternatively, an accurate angular error output can be obtained irrespective of the radial position of the disk of the optical pickup.

[0007]

FIG. 1 is a circuit diagram showing a tilt servo device in an optical video disk player showing one embodiment of the present invention.

In FIG. 1 , reference numeral 1 denotes a tilt sensor comprising a light emitting diode 2 for emitting infrared rays to a disk 5 and two-segment photodiodes 3 and 4 for receiving the reflected light of the infrared rays reflected by the disk 5. It is. The tilt sensor 1 is fixed to an optical pickup (not shown), and is moved in the radial direction of the disk 5 together with the optical pickup.

Reference numerals 6 and 7 denote the two sensors of the tilt sensor 1 , respectively.
A current / voltage conversion amplifier for converting each light reception output of the divided photodiodes 3 and 4 from a current signal to a voltage signal, and 8 subtracts each light reception output of the voltage signal converted by each of the current / voltage conversion amplifiers 6 and 7. The subtraction circuit 9 is an addition circuit for adding the respective light receiving outputs of the voltage signals converted by the current / voltage conversion amplifiers 6 and 7, respectively.

Here, when the angle of the optical axis of the light beam of the optical pickup with respect to the vertical direction of the disk is 0 degree, the tilt sensor 1 outputs the respective light receiving outputs of the two-part photodiodes 3 and 4. It is adjusted so that the difference between the respective light receiving outputs increases as the angle deviates from 0 degree, and the polarity of the difference between the respective light receiving outputs is inverted depending on the direction in which the angle occurs. ing.
Therefore, the voltage level changes linearly from the subtraction circuit 8 in accordance with the error amount of the inclination angle of the optical axis of the light beam of the optical pickup from the perpendicular to the disk, and the polarity differs depending on the direction of the inclination angle. An angle error output is generated.

The addition circuit 9 calculates the sum of the respective light receiving outputs of the two-division photodiodes 3 and 4, so that the two
A reflected light amount output which is the sum of the reflected light amounts received by the divided photodiodes 3 and 4 is generated.
Increases or decreases according to the distance between the tilt sensor 1 and the disk 5,
The voltage level changes linearly according to the distance.

Reference numeral 10 denotes a servo switch for switching on / off of the tilt servo system, and 11 denotes the servo switch.
A servo switching control circuit 12 for controlling the switching of the servo switch 10, a hysteresis circuit 12 for giving the hysteresis characteristic to the angular error output generated from the subtraction circuit 8 when the servo switch 10 is on, and 13 for correcting the tilt of the optical pickup. A tilt mechanism 14 is a tilt motor serving as a drive source of the tilt mechanism 13, and 15 is a tilt motor drive circuit that drives the tilt motor 14 in accordance with an angle error output given a hysteresis characteristic by the hysteresis circuit 12.

Reference numeral 16 denotes a comparison circuit for comparing the output of the amount of reflected light generated from the addition circuit 9 with a preset reference voltage 17. Here, the reference voltage 17 is set in consideration of the voltage level of the standard reflected light amount output from the adder circuit 9 in a range where the light receiving characteristics of the two-division photodiodes 3 and 4 are good.

Reference numeral 18 denotes an LED drive circuit for driving the light emitting diode 2 of the tilt sensor 1 in accordance with the comparison output generated from the comparison circuit 16, and 19 denotes a current limiting resistor for limiting a current flowing through the light emitting diode 2. is there.

Next, the operation of the circuit shown in FIG. 1 will be described.

The mounting angle of the tilt sensor 1 is adjusted so that the light receiving output currents of the two divided photodiodes 3 and 4 become equal when the optical axis of the light beam from the optical pickup is perpendicular to the disk surface. Have been. When the optical pickup is reading a signal from the disk, a light receiving output is generated from each of the two-division photodiodes 3 and 4. An angle error output corresponding to the inclination angle of the optical axis of the optical beam of the optical pickup with respect to the disk with respect to the disk is generated.

The servo switch 10 is turned on by the servo switching control circuit 11 in a state in which the signal of the disk is normally read by the optical pickup and the signal is being reproduced. Therefore, the angle error output generated from the subtraction circuit 8 is supplied to the hysteresis circuit 12 via the servo switch 10, and the hysteresis circuit 12 gives a hysteresis characteristic. The angle error output with the hysteresis characteristic is
Since the control signal is supplied to the tilt motor drive circuit 15 and becomes a control signal for operating the tilt motor drive circuit 15, the tilt motor 14 is driven according to the angle error output, and the tilt mechanism 13 is displaced according to the angle error output. Is done.

Therefore, when the absolute value of the voltage level of the angle error output generated from the subtraction circuit 8 reaches a predetermined value,
The angle of the optical pickup is displaced according to the polarity of the voltage level so that the voltage level of the angle error output becomes “0”, and the optical axis of the light beam of the optical pickup is perpendicular to the disk surface. It is held with a certain dead zone.

The light receiving outputs from the two-divided photodiodes 3 and 4 are converted into voltage signals by current / voltage conversion amplifiers 6 and 7, respectively, and then added by an adder circuit 9. And 4, a reflected light quantity output corresponding to the reflected light quantity received is generated. The voltage difference between the reflected light amount output and the reference voltage 17 is compared by a comparison circuit 16, and a comparison output corresponding to the voltage difference is generated from the comparison circuit 16. Then, the LED drive circuit 18 is controlled by the comparison output. Therefore, the drive current supplied to the light emitting diode 2 is controlled according to the comparison output, and the light emission amount of the light emitting diode 2 is changed according to the comparison output.

Therefore, the amount of light emitted from the light emitting diode 2 is controlled so that the sum of the amounts of reflected light received by the two-part photodiodes 3 and 4 becomes constant.

When the tilt mechanism 13 is displaced so that the optical axis of the light beam of the optical pickup is perpendicular to the disk surface, the optical pickup slides in the radial direction with the tilt mechanism 13 displaced. When moving, the distance between the tilt sensor 1 and the disk 5 changes not less than a little due to the displacement. When the distance between the tilt sensor 1 and the disk 5 changes, if the amount of light emitted from the light emitting diode 2 of the tilt sensor 1 is constant, the amount of reflected light received by the two-part photodiodes 3 and 4 is large. Decreases, and increases as the distance decreases. And
When the amount of reflected light increases or decreases, even if the inclination angle of the optical axis of the optical beam of the optical pickup from the perpendicular to the disk is the same, the light receiving outputs of the two-part photodiodes 3 and 4 increase or decrease according to the increase or decrease in the amount of reflected light. Therefore, even if the ratio of the respective light receiving outputs is the same, the subtraction circuit 8 generates an angle error output of a different voltage level. Therefore, when the amount of reflected light increases or decreases, the hysteresis circuit 12
The inclination angle of the dead zone given by the above will be different.

However, in the circuit of FIG. 1, as described above, the sum of the amounts of reflected light received by the two-part photodiodes 3 and 4 is kept constant, and therefore, the displacement of the tilt mechanism 13 or the tilt mechanism Even if 13 is the same displacement amount, even if the distance between the tilt sensor 1 and the disk 5 changes due to the radial sliding position of the optical pickup, the optical axis of the light beam of the optical pickup is perpendicular to the disk surface. If the angle of inclination from is the same, there is almost no change in the current level of each light receiving output of the two-division photodiodes 3 and 4. Therefore, regardless of the distance between the tilt sensor 1 and the disk 5, the subtraction circuit 8 generates an accurate angle error output according to the tilt angle.

Therefore, the dead zone generated in the tilt mechanism 13 due to the hysteresis circuit 12 providing the hysteresis characteristic to the angle error output is determined by the tilt mechanism 13
Irrespective of the amount of displacement, the range of the inclination angle is constant.

[0024]

As described above, the tilt servo device according to the present invention controls the amount of light received by the light receiving element of the tilt sensor in accordance with the amount of light reflected from the disk and received by the light receiving element of the tilt sensor. Is constant, so regardless of the distance between the tilt sensor and the disc,
An accurate angle error output can be obtained, and even if the displacement amount of the tilt mechanism and the sliding position of the optical pickup change, the angle range of the dead zone in the inclination angle of the optical axis of the optical beam of the optical pickup with respect to the disk from the disk is changed. It is kept constant, and the increase in the angle range of the dead zone can prevent an increase in leakage of the light beam from the optical pickup to the adjacent track.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention.

[Description of Signs] 1 tilt sensor 2 light emitting diode 3, 4 split photodiode 8 subtraction circuit (angle error output generation circuit) 9 addition circuit (reflected light quantity output generation circuit) 12 hysteresis circuit 13 tilt mechanism 16 comparison circuit

Claims (1)

(57) [Claims] 1. A tilt servo device for an optical disk player for driving a tilt mechanism for displacing the tilt of an optical pickup and controlling the optical axis of a light beam of the optical pickup to be perpendicular to the disk. A light-receiving element for receiving light reflected by the disk, and a light spot received by the light-receiving element to generate a sensor output corresponding to the angle of the light beam of the optical pickup with respect to the disk. A tilt sensor, an angle error output generation circuit that generates an angle error output according to a tilt angle of the light beam of the optical pickup from a perpendicular to the disk using a sensor output from the tilt sensor, and an angle error output generation circuit. A hysteresis circuit for providing a hysteresis characteristic to the angular error output of A reflected light amount output generating circuit for generating a reflected light amount output according to the reflected light amount from the disk using a sensor output from the tilt sensor, and driving the tilt mechanism according to the angle error output obtained via the hysteresis circuit. A tilt servo device for an optical disc player, wherein the amount of light emitted from the light emitting element of the tilt sensor is controlled in accordance with the amount of reflected light output from the reflected light amount output generating circuit.