JPH07235064A - Method for automatically balance adjusting position senser and circuit therefor - Google Patents

Abstract

PURPOSE:To provide a method and circuit for automatically adjusting the balance of a position senser automatically correcting offset in the position senser. CONSTITUTION:Output of one side photodetector 26a of the position senser 27 is inputted to inversion input terminal of a subtracter 44 through an amplifier 41, and the output of the other side photodetector 26b is inputted to non- inversion input terminal of the subtracter 44 through an amplifier 42 and a gain adjustment circuit 43. Further, the gain of the gain adjustment circuit 43 is set by a CPU 48 and a D/A converter 46 so that the position senser output outputted from the subtracter 44 becomes zero when an objective lens 21 is located at a neutral point. Thus, the correct position senser output is obtained always even when the temp. change and the change with time occur, and a correct tracking error signal TE is obtained always.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic balance adjusting method for a position sensor for detecting an amount of deviation of an objective lens of an optical disk device and its circuit.

[0002]

2. Description of the Related Art Conventionally, when recording information on an optical disc or reproducing information from the optical disc, a laser beam is emitted from an optical pickup along a track formed on the optical disc. At this time, it is well known that there are roughly two types of tracking methods for making the irradiation position of the laser beam follow the track, namely, the three-beam method and the one-beam push-pull method.

Further, there is also a tracking control device using a mechanism for displacing the position of the objective lens in the optical pickup in the radial direction of the optical disc in order to improve the tracking accuracy of the track, and a position sensor for detecting the deviation amount of the objective lens. It is used. For example, as shown in FIG.
The optical pickup 10 includes an objective lens actuator 2
0 is provided so that the position of the objective lens 21 can be moved left and right with respect to the track.

That is, the objective lens 21 is fixed to one end of the swing rod 22, and the LED 2 is attached to the other end of the swing rod 22.
3 is fixed, and a pivot shaft 24 is provided at the center of the swing rod 22. The swing rod 22 can be rotated about a rotation shaft 24 by an electromagnetic force of a drive coil (not shown) and a magnet. Further, rubber dampers 25 are provided on the left and right of the objective lens 21, and normally the objective lens 21 is supported so as to be positioned at a neutral point. Furthermore, when the objective lens 21 is located at the neutral point, it is arranged so as to face the light emitting surface of the LED 23.
A position sensor 27 composed of divided photodetectors 26a and 26b is provided.
The position of the objective lens 21, that is, the amount of deviation can be detected by the amount of light received by 26b.

On the other hand, a well-known four-divided photodetector 11 is used as the photodetector 11 for receiving the reflected light from the optical disk, and the total amount of light received by the detectors 11a and 11d located on the left side of the track and the detector 11b located on the right side of the track. , 11c corresponding to the total amount of received light V1 and V2 are generated by the summing amplifiers 31 and 32, and the added value of these voltages V1 and V2 is the read signal (RF).
The signal) is output from the adder 33. Also, the voltage V
The difference voltage V3 of 1 and V2 is generated by the subtractor 34, and the difference voltage Vc of the output voltages Va and Vb from the photodetectors 26a and 26b of the position sensor is generated by the subtractor 35 and the voltage V3. The difference voltage of the voltage Vc is the subtractor 3
6 and is output as a tracking error signal TE. Here, the LED of the position sensor is always turned on with a constant brightness, and the output voltages Va and Vb of the photodetectors 26a and 26b change in accordance with the deviation amount of the objective lens 21.

Here, the offset voltage Vof and the voltage Vc at the voltage V3 change according to the amount of deviation of the objective lens, as shown in FIG. Therefore, the offset of the tracking error signal TE due to the displacement of the objective lens 21 can be removed by obtaining the difference between the voltage V3 and the voltage Vc and using this as the tracking error signal TE.

[0007]

However, the one-beam push-pull method described above can be realized by a simple optical system,
Although it is low in cost, it has a drawback that tracking offset is likely to occur in principle. For example, due to temperature change or secular change, warping of the swing rod 22 or the like occurs, and
The D23 and the photodetectors 26a and 26b are misaligned, a position sensor offset is generated, and the tracking offset is changed.

In view of the above problems, it is an object of the present invention to provide a position sensor automatic balance adjustment method and circuit for automatically correcting the offset of the position sensor.

[0009]

In order to achieve the above-mentioned object, the present invention provides an optical pickup having an objective lens movable in the tracking direction, and when the objective lens is located at a neutral point. Position sensor automatic balance adjustment of an optical disk device provided with position sensors having two signal output means for outputting signals of equal level to each other and each signal level changing in different directions according to the amount of deviation of the objective lens. A position sensor automatic balance adjusting method for correcting at least one signal level so that output signal levels from the two signal output means become equal when the objective lens is positioned at a neutral point. suggest.

According to a second aspect of the present invention, an optical pickup having an objective lens that is movable in the tracking direction and signals that are at the same level as each other are output when the objective lens is located at the neutral point, and the deviation of the objective lens is detected. A position sensor automatic balance adjustment circuit of an optical disk device comprising a position sensor having two signal output means in which respective signal levels change in different directions according to the amount, the lens positioning the objective lens at a neutral point. Position setting means,
Level difference detecting means for detecting the difference between the signal levels output from the two signal output means, and the level difference detecting means for detecting when the objective lens is positioned at the neutral point by the lens position setting means. There is proposed a position sensor automatic balance adjustment circuit comprising level correction means for correcting the output signal level of at least one of the signal output means so that the level difference becomes zero.

[0011]

According to the first aspect of the present invention, the objective lens of the position sensor having two signal output means in which each signal level changes in different directions corresponding to the deviation amount of the objective lens is located at the neutral point. Then, the output signal levels from at least one of the signal output means are corrected so that the output signal levels from the two signal output means become equal. As a result, an accurate position sensor output can always be obtained.

According to the second aspect, when the objective lens is located at the neutral point, the signals of the same level are output to each other,
The objective lens of the position sensor having two signal output means in which each signal level changes in different directions corresponding to the deviation amount of the objective lens is positioned at the neutral point by the lens position setting means, and in this state The difference between the signal levels output from the two signal output means is detected by the level difference detection means. Further, when the objective lens is positioned at the neutral point by the lens position setting means,
The level correction means corrects the output signal level of at least one of the signal output means so that the level difference detected by the level difference detection means becomes zero. As a result, an accurate position sensor output can always be obtained.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, the same components as those of the above-described conventional example are designated by the same reference numerals and the description thereof is omitted. Further, the difference between the conventional example and the present embodiment is that a position sensor automatic balance adjustment circuit (hereinafter referred to as a balance adjustment circuit) 40 is provided in place of the subtractor 35.

That is, the balance adjusting circuit 40 includes the amplifier 4
1, 42, gain variable circuit 43, subtractor 44, analog switch 45, digital / analog (hereinafter referred to as D / A) converter 46, analog / digital (hereinafter referred to as A)
/ D) and a CPU 48. Further, the variable gain circuit 43 includes a triangular wave generator 51,
It is composed of an adder 52, a comparator 53, an analog switch 54, and a low-pass filter 55.

The amplifier 41 amplifies the output voltage Va of the photodetector 26a and outputs it to the inverting output terminal of the subtractor 44. Further, the amplifier 42 amplifies the output voltage Vb of the photodetector 26b and outputs it to the first contact 54a of the analog switch 54. The output terminal of the subtractor 44 is the subtractor 3
The digital data output from the A / D converter 47 is connected to the inverting input terminal 6 and the input terminal of the A / D converter 47, and is input to the CPU 48. Digital data output from the CPU is input to the D / A converter 46, and the output terminal of the D / A converter 46 is connected to the second contact 45b of the analog switch 45. here,
The first contact 45a of the analog switch 45 is grounded.

Further, in the variable gain circuit 43,
The triangular wave output from the triangular wave generator 51 is input to one input terminal of the adder 52, and the other input terminal is connected to the contact piece 45c of the analog switch 45. Adder 5
The output terminal of 2 is connected to the non-inverting input terminal of the comparator 53, and a predetermined threshold voltage Vth is applied to the inverting input terminal. Further, the output signal of the comparator 53 is input to the analog switch 54, and the analog switch 54 has its contact piece 54c when the output signal of the comparator 53 is at a high level.
Is connected to the second contact 54b and the contact piece 5 is
4c is connected to the first contact 54a. The second contact 54b of the analog switch 54 is grounded, and the contact piece 54c is connected to the non-inverting input terminal of the subtractor 44 via the low-pass filter 55.

Next, the operation of this embodiment having the above-mentioned structure will be described. In order to automatically remove the offset of the position sensor 27, the CPU 48 switches the analog switch 45 every predetermined time based on the program to perform automatic balance adjustment. That is, when performing automatic balance adjustment, the CPU 48 first drives the drive coil, magnet, and the like (not shown) of the objective lens actuator 20 to maintain the objective lens 21 at the neutral point. Next, the CPU 48 causes the contact piece 45c of the analog switch 45.
Is connected to the first contact 45a, and A /
The output value of the D converter 47 is read. At this time, the subtractor 44
Corresponds to the offset of the position sensor 27, and the output value of the A / D converter 47 at this time is the CPU
Read 48.

Thereafter, the CPU 48 controls the A / D converter 47.
The same value as that read from is output again to the D / A converter 46, and the contact piece 45c of the analog switch 45 is connected to the second contact 45b. As a result, the read offset value is added to the triangular wave voltage by the adder 52, the output signal of the comparator 53 has a high level ratio higher than the low level, and the analog switch 54 has a contact piece 54c and a second contact point. The connection ratio will increase. Therefore, the output signal level of the low pass filter 55 decreases, the output of the subtractor 44 becomes zero, and the offset of the position sensor 27 is removed. In this state, subsequent tracking processing and the like are performed.

As described above, the offset of the position sensor 27 is removed, and the accurate position sensor output PS can always be obtained.
Even if the swing rod 22 is warped or the like and the LED 23 and the photo detectors 26a and 26b are displaced from each other, the position sensor offset does not occur, and an accurate tracking error signal TE can always be obtained. As a result, the track search can be stably performed, and the jitter at the time of recording / reproducing the data can be reduced.

[0020]

As described above, according to claim 1 of the present invention, the output signals from at least one of the signal output means of the position sensor are equalized so that the output signal levels from the two signal output means become equal. Since the level is corrected, an accurate position sensor output can always be obtained even if a temperature change or a secular change occurs, and an accurate tracking error signal TE can always be obtained.

According to a second aspect of the present invention, the level correction means corrects the output signal level from at least one of the signal output means so that the output signal levels from the two signal output means of the position sensor become equal. Therefore, an accurate position sensor output can always be obtained even if a temperature change or a secular change occurs, and an accurate tracking error signal TE can always be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a conventional example.

FIG. 3 is a diagram for explaining the relationship between the amount of deviation of the objective lens and each voltage.

[Explanation of symbols]

10 ... Optical pickup, 11 ... Photo detector, 20
... Objective lens actuator, 21 ... Objective lens, 22
... rocking rod, 23 ... LED, 24 ... rotary shaft, 25 ... rubber damper, 26a, 26b ... photodetector, 27 ... position sensor, 31, 32 ... summing amplifier, 33 ... adder, 34, 35, 36 ... subtraction Vessel, 40 ... Position sensor automatic balance adjustment circuit, 41, 42 ... Amplifier, 43 ...
Gain adjusting circuit, 44 ... Subtractor, 45 ... Analog switch, 46 ... D / A converter, 47 ... A / D converter, 48 ...
CPU, 51 ... Triangle wave generator, 52 ... Adder, 53 ... Comparator, 54 ... Analog circuit, 55 ... Low-pass filter.

Claims (2)

[Claims] 1. An optical pickup having an objective lens movable in a tracking direction, and when the objective lens is located at a neutral point, outputs signals of the same level to each other, corresponding to a deviation amount of the objective lens. A position sensor automatic balance adjusting method for an optical disc device, comprising: a position sensor having two signal output means in which respective signal levels change in different directions, wherein the objective lens is positioned at a neutral point; A position sensor automatic balance adjusting method, characterized in that at least one signal level is corrected so that output signal levels from two signal output means become equal. 2. An optical pickup having an objective lens movable in a tracking direction, and when the objective lens is located at a neutral point, outputs signals of the same level to each other, corresponding to the amount of deviation of the objective lens. A position sensor automatic balance adjustment circuit for an optical disc apparatus, comprising: a position sensor having two signal output means for changing respective signal levels in different directions, the lens position setting means for positioning the objective lens at a neutral point; Level difference detection means for detecting a difference between signal levels output from the two signal output means; and the level difference detection means when the objective lens is positioned at the neutral point by the lens position setting means. Level correction means for correcting the output signal level of at least one of the signal output means so that the level difference becomes zero. Position sensor automatic balance adjustment circuit characterized by consisting of and.