JPH08180443A - Optical pickup for optical disk device - Google Patents

Abstract

PURPOSE: To facilitate optical axis adjustment of an objective lens. CONSTITUTION: A focus driving signal DF is amplified by an operational amplifier 23a, and a focusing coil 20a is driven with a current by an operational amplifier 23b with the amplified focus driving signal DF. The amplified focus driving signal DF and a voltage generated by a jitter voltage conversion circuit 27 are added up and inputted to an operational amplifier 23c, and hence a focusing coil 20b is current-driven. Then, the voltage generated by the jitter voltage conversion circuit 27 is inputted to an operational amplifier 23d, and hence a bias coil 20c is current-driven. Thus, by the current driving of the focusing coils 20a and 20b and the bias coil 20c, deviation of the optical axis of the objective lens from the surface of an optical disk and a track is automatically adjusted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup for an optical disk device in which the optical axis of an objective lens can be easily adjusted.

[0002]

2. Description of the Related Art As a conventional method for adjusting an objective lens of an optical pickup of an optical disk device, a mechanical adjusting method is generally used. FIG. 5 is a configuration diagram of an optical pickup of a conventional optical disc device, and the configuration and adjustment method will be described below.

The optical pickup comprises an objective lens assembly 1 and a carriage 2. The objective lens assembly 1 is
The objective lens 3, the objective lens actuator 4, and the laser starting mirror 5 are incorporated, and a convex portion 7 formed of a part of a sphere having a radius R centered on the objective lens 3 is provided at the center of the lower surface of the bottom plate 6. are doing. Further, on the upper surface of the bottom plate 9 of the box portion 8 of the carriage 2, a concave mount 10 corresponding to the convex portion 7 is formed.

The objective lens assembly 1 is housed in the box portion 8 of the carriage 2, and the convex portion 7 is placed on the mounting base 10 by a plurality of screws 11 from the bottom plate 6 side of the carriage 2. A portion around the convex portion 7 is attached by screwing.

The adjustment for making the optical axis 12 of the objective lens 3 perpendicular to the surface of the mounted optical disk 13 is performed through an opening 16 formed in the chassis base 15 of the optical disk device main body 14 through the chassis base. This is done by tightening or loosening the screw 11 from the lower surface of 15 using a screwdriver as appropriate. By operating the screw 11 in this manner, the objective lens assembly 1 is slightly rotated about the contact portion between the convex portion 7 and the mounting base 10, and the inclination of the optical axis 12 is adjusted. After the adjustment, the screw 11 is adhesively fixed.

[0006]

SUMMARY OF THE INVENTION In the above conventional configuration,
The adjustment angle of the optical axis 12 corresponds to the rotation angle of the screw 11. However, it is difficult to accurately determine the rotation angle of the screw 11 and it takes time.
There is a problem that it is difficult to perform the adjustment of 2 with high accuracy in a short time.

Therefore, the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide an optical pickup of an optical disk device capable of automatically adjusting the optical axis of an objective lens.

[0008]

To this end, the present invention is directed to an optical disk apparatus provided with an objective lens and a lens holder which holds the objective lens and can be finely moved in the optical axis direction of the objective lens and in the radial direction of the optical disk. A plurality of focusing coils that separately drive both ends of the lens holder in the optical axis direction of the objective lens, and a tracking coil that drives the lens holder in a direction orthogonal to the optical axis direction of the objective lens. A bias coil that adjusts the optical axis in a direction perpendicular to the tangent to the track of the optical disc, a permanent magnet that forms a magnetic field that crosses the focusing coil, the tracking coil, and the bias coil, a yoke that forms a magnetic circuit, and a plurality of focusing coils. Drive the tracking coil and a plurality of drive circuits that generate driving force to drive the Driving circuit for generating a driving force for driving the bias coil, a bias current generating circuit for generating a driving force for driving the bias coil provided in at least one of the driving circuits for the focusing coil, and the optical axis of the objective lens for reading the data read signal from the optical disc. It has a control circuit that controls to minimize the amount of jitter, and controls so that the optical axis of the objective lens with respect to the surface of the mounted optical disk is in the track tangential direction and the optimum direction with respect to the direction perpendicular to the track tangent line. A bias current obtained from a bias current generating circuit connected to the circuit is supplied to a bias coil to forcibly displace the objective lens.

[0009]

According to the present invention, the bias current generating circuit is provided in at least one of the driving circuits of the focusing coil, and the optical axis of the objective lens is perpendicular to the surface of the mounted optical disk. A bias current is made to flow from the circuit to the bias coil, and the objective lens is forcibly displaced so as to minimize the amount of jitter of the data read signal of the optical disc by the control circuit, so the optical axis adjustment is automatically performed without a mechanical adjustment process. Can be done.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of an optical pickup of an optical disc device according to an embodiment of the present invention, FIG. 2 is a drive circuit diagram of the optical pickup of the optical disc device, and FIG. 3 is a jitter-voltage conversion circuit diagram of the optical pickup of the optical pickup device. And a timing chart, and FIG. 4 is an explanatory diagram of the optical axis adjustment of the objective lens of the optical pickup of the optical disc device.

In FIG. 1, (a) is a front view of the optical pickup, (b) is a side view thereof, and (c) is a top view thereof.
Reference numeral 17 is an objective lens, 18 is a lens holder that holds the objective lens 17, and 19 is four parallel four wires for supporting the lens holder 18, which are fixed to a carriage (not shown). 20a and 20b are focusing coils, 20c is a bias coil, and 21a and 2a.
Reference numerals 1b and 21c are yokes for forming a magnetic circuit, and 22
Reference numerals a, 22b and 22c are permanent magnets. In FIG.
Reference numerals 23a, 23b, 23c and 23d are operational amplifiers, 24 is an optical pickup, 25 is a binarization circuit, 26 is a PLL circuit, and 27 is a jitter-voltage conversion circuit. In FIG. 3, (a) is a circuit diagram of the jitter-voltage conversion circuit, (b) is the same timing chart, 28 and 31 are constant current sources,
29 and 30 are switches, 32 is a capacitor, 33 is a buffer, 34 is an operational amplifier, and 35 is zero jitter. In FIG. 4, 24 is an optical pickup, 36 is an optical disc, 3
7 is a motor.

Optical pickup 2 constructed as described above
The operation of No. 4 will be described on the assumption that there is no deviation of the optical axis from the objective lens 17. In FIG. 1, the objective lens 1
In order to drive 7 to a predetermined position, each of the focusing coils 20a and 20b is current-driven. The focusing coils 20a and 20b generate driving forces f1 and f2 in the optical axis direction, respectively, according to Fleming's left-hand rule, and the resultant force F drives the lens holder 18 to a predetermined position along the optical axis direction.

Next, as shown in FIG. 4, the optical pickup 24
And FIG. 2, the adjustment method when the deviation θ of the optical axis occurs
This will be described with reference to FIG. First, in order to displace the objective lens 17 to the adjustment position, the focus drive signal DF in FIG. 2 is generated. The focus drive signal DF is amplified by the operational amplifier 23a and is then amplified by the operational amplifiers 23b and 23c.
Respectively. Focusing coils 20a, 20 connected to output terminals of operational amplifiers 23b, 23c
b is current-driven by a constant current by the operational amplifiers 23b and 23c. Focusing coils 20a, 2
0b generates driving forces f1 and f2 in the optical axis direction according to Fleming's left-hand rule as described above, and the resultant force F drives the lens holder 18 to a predetermined position along the optical axis direction.

The optical pickup 2 at the adjustment position shown in FIG.
The adjustment of the deviation θ from the tangential direction of the track with respect to the surface of the optical disc 36 of No. 4 is performed by adding the voltage obtained by the jitter-voltage conversion circuit 27 to the focus drive signal DF amplified by the operational amplifier 23a and setting the operational amplifier 23c. The focusing coil 20b is current-driven via this. A driving force corresponding to a bias current is generated in the focusing coil 20b in accordance with Fleming's left-hand rule, which causes displacement, and the optical pickup 24 shown in FIG. Can be adjusted.

Next, the optical disc 36 of the optical pickup 24
To adjust the deviation θ from the plane perpendicular to the track tangent line, the voltage obtained by the jitter-voltage conversion circuit 27 is input to the operational amplifier 23d, and the bias coil 20c is current-driven. In the bias coil 20c, a driving force corresponding to a bias current is generated according to Fleming's left-hand rule, which causes a displacement to cause an optical disc 36 of the optical pickup 24.
It is possible to adjust the deviation θ from the direction perpendicular to the track tangent to the plane of.

The operation of the jitter-voltage conversion circuit 27 will be described with reference to FIG. Data and read clocks RCLK1 to 3 are output from the PLL circuit 26. Switch 29
Read clock RCL1 from the rising edge of data
The switch 30 is turned on from the rising edge of the read clocks RCLK1 to the falling edge of the data. Therefore, the capacitor 32
Is charged by the current of the constant current source 28 when the switch 29 is ON, and discharged by the current of the constant current source 31 when the switch 30 is ON. The output voltage of the capacitor 32 is the buffer 3
3 is input to the operational amplifier 34. Resistance R10,
The voltage divided by R11 is the read clock RCLK.
The jitter at the rising edge of 1 is equal to the output voltage from the buffer 33 at 0 point T. The output of the buffer 33 is passed through a low pass filter composed of an operational amplifier 34 to convert the jitter into a voltage. Therefore, when the read clock is RCLK1, the voltage of the capacitor 32 becomes 0, when RCLK2, it becomes a negative voltage, and when RCLK3, it becomes a positive voltage.

According to the embodiments as described above, the optical axis of the objective lens can be automatically and easily adjusted without mechanical adjustment.

[0018]

According to the present invention, by varying the bias current value, the deviation of the optical axis between the direction of the track of the objective lens with respect to the optical disk surface and the direction perpendicular to the track tangent is automatically adjusted without mechanical adjustment. It is possible to provide an optical pickup of an optical disk device which does not cause a loss of adjustment / bonding time due to mechanical adjustment because it can be adjusted easily and accurately.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an optical pickup of an optical disc device according to an embodiment of the present invention.

FIG. 2 is a drive circuit diagram of an optical pickup of an optical disc device according to an embodiment of the present invention.

FIG. 3 is a jitter-voltage conversion circuit diagram and timing chart of the optical pickup of the optical pickup device according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram of optical axis adjustment of an objective lens of an optical pickup of an optical disc device according to an embodiment of the present invention.

FIG. 5 is a configuration diagram of an optical pickup of a conventional optical disc device.

[Explanation of symbols]

 17 Objective Lens 18 Lens Holder 19 4 Wires 20a, 20b Focusing Coil 20c Bias Coil 21a, 21b, 21c Yoke 22a, 22b, 22c Permanent Magnets 23a, 23b, 23c, 23d Operational Amplifier 24 Optical Pickup 25 Binarization Circuit 26 PLL Circuit 27 Jitter-voltage conversion circuit 28 Constant current source 29 Switch 30 Switch 31 Constant current source 32 Capacitor 33 Buffer 34 Operational amplifier 35 Jitter 0 point 36 Optical disk 37 Motor

Claims (2)

[Claims] 1. An optical pickup for an optical disc apparatus, comprising: an objective lens; and a lens holder that holds the objective lens and can be finely moved in the optical axis direction of the objective lens and in the radial direction of the optical disc. A plurality of focusing coils for separately driving both ends of the lens holder in the optical axis direction, a tracking coil for driving the lens holder in a direction orthogonal to the optical axis direction of the objective lens, and a perpendicular to the tangent line of the track of the optical disc. A bias coil that adjusts the optical axis in a direction, a permanent magnet that forms a magnetic field that crosses the focusing coil, the tracking coil, and the bias coil, a yoke that forms a magnetic circuit, and the plurality of focusing coils that are driven separately. Drive circuit for generating a driving force for driving the tracking coil and a driving circuit for driving the tracking coil. A drive circuit for generating force, a bias current generation circuit for generating drive force provided in at least one of the drive circuits for the focusing coil, and the optical axis of the objective lens minimizes the amount of jitter in the data read signal of the optical disc. And an optical axis of the objective lens with respect to the surface of the mounted optical disc, the optical axis of the objective lens being connected to the control circuit so as to be in the optimum direction with respect to the track tangential direction and the direction perpendicular to the track tangential line. An optical pickup for an optical disk device, wherein a bias current obtained from a bias current generating circuit is supplied to the bias coil to forcibly displace the objective lens. 2. The control circuit obtains an optimum bias current from a jitter amount by a jitter-voltage conversion circuit having a constant current source for charging / discharging a capacitor, a changeover switch, and a reduction filter. An optical pickup for the optical disk device described.