JPH07326056A - Optical pickup of optical disk device - Google Patents

Abstract

PURPOSE:To obtain an optical pickup of an optical disk device capable of easy making optical axis adjustment of the objective lens of the optical pickup of the optical disk device. CONSTITUTION:A focus driving signal S is amplified by an operational amplifier 23a and a focusing coil 20b is subjected to current driving with an operational amplifier 23b by the amplified focus driving signal S. The amplified focus driving signal S and the bias current regulated by a half-fixed resistor VRm are added and inputted to the operational amplifier 23c and a focusing coil 20a is subjected to current driving. The bias current regulated by a half-fixed resistor VRn is inputted to an operational amplifier 23d, by which a bias coil 20c is subjected to current driving.

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 which can easily adjust an optical axis of an objective lens.

[0002]

2. Description of the Related Art A mechanical adjustment method is generally used as an objective lens adjustment method for an optical pickup of a conventional optical disk device. 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 includes an objective lens assembly 1
And carriage 2. Objective lens assembly 1
Includes an objective lens 3, an objective lens actuator 4, and a mirror 5 for raising a laser, and a convex portion 7 formed of a part of a sphere having a radius R centered on the objective lens 3 at the center of the lower surface of the bottom plate 6. have. 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.
Thus, it is attached by screwing at a portion around the convex portion 7.

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 in which the optical axis of an objective lens can be easily adjusted.

[0008]

To this end, the present invention provides an objective lens and a lens holder that holds the objective lens and is supported so as to be finely movable in the optical axis direction of the objective lens and in the radial direction of the optical disk. In an optical pickup of an optical disc device including a focusing coil for separately driving both ends of the lens holder in the optical axis direction of the objective lens, and a tracking coil for driving in a direction orthogonal to the optical axis direction of the objective lens. A coil, a bias coil for adjusting the optical axis of the optical disc in the direction perpendicular to the track, a permanent magnet that forms a magnetic field across the focusing coil, the tracking coil, and the bias coil, a yoke, and a separate driving of the focusing coil. To drive the tracking coil and the two drive circuits that generate the driving force. A drive circuit that generates a force, a bias current generation circuit that generates a drive force for driving the bias coil, and a bias current generation circuit in at least one of the focusing coil drive circuits. A bias current is made to flow from the bias current generating circuit so that the track tangent line and the vertical direction are perpendicular to the surface of the mounted optical disk, and the objective lens can be forcibly displaced.

[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 bias current generating circuit is arranged so that the optical axis of the objective lens is perpendicular to the surface of the mounted optical disk. Since the bias current is made to flow from the circuit to forcibly displace the objective lens, the optical axis can be easily adjusted without any mechanical adjustment process.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. 1A, 1B and 1C are configuration diagrams 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.
4 (a) and 4 (b) and FIGS. 4 (a) and 4 (b) are explanatory views of the optical axis adjustment of the objective lens of the optical pickup of the optical disc device. In FIG. 1, 17 is an objective lens, 18 is a lens holder that holds the objective lens 17, and 19 is four parallel 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, 21
Reference numerals a, 21b and 21c are yokes for forming a magnetic circuit, and 22a, 22b and 22c are permanent magnets. Also,
In FIG. 2, 23a, 23b, 23c and 23d are operational amplifiers, and VRm and VRn are semi-fixed resistors for generating bias current.

The principle of operation of the optical pickup constructed as described above will be explained on the assumption that there is no deviation of the optical axis from the objective lens 17. In order to drive the objective lens 17 to a predetermined position, the focusing coils 20a and 20b are 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, an adjusting method when the optical axis is displaced from the objective lens 17 as shown in FIGS. 3A and 3B will be described with reference to FIGS. 1, 2 and 3. First, in order to displace the objective lens 17 to the adjustment position, the focus drive signal S is generated in FIG. The focus drive signal S is amplified by the operational amplifier 23a and is then amplified by the operational amplifiers 23b and 23c.
Are input 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 in accordance with 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. To adjust the deviation θ1 of the objective lens 17 from the optical disc surface in the track tangential direction at the adjustment position shown in FIG. The bias current is added to the focus drive signal S amplified by the operational amplifier 23a, and the focusing coil 20a is current-driven via the operational amplifier 23c. Focusing coil 2
In 0a, a driving force fR corresponding to a bias current is generated according to Fleming's left-hand rule, which causes displacement, and
As shown in (b), the deviation θ1 from the optical disc surface of the objective lens 17 with respect to the track tangential direction can be adjusted.

Next, in the adjustment position shown in FIG. 4A, the deviation θ2 of the objective lens 17 from the optical disc surface in the direction perpendicular to the track is adjusted by adjusting the semi-fixed resistance V for bias current generation.
The resistance value of Rn is variably adjusted, a desired bias current is input to the operational amplifier 23d, and the bias coil 20c is current-driven. In the bias coil 20c, a driving force f3 corresponding to a bias current is generated according to Fleming's left-hand rule, which causes a displacement to cause the objective lens 1 as shown in FIG.
Deviation from the direction perpendicular to the track with respect to the optical disk surface of 7
2 can be adjusted. As described above, according to each embodiment, the optical axis of the objective lens 17 can be easily adjusted without mechanical adjustment.

[0014]

According to the present invention, by varying the bias current value, the deviation of the optical axis of the objective lens from the track tangent to the optical disk surface and the vertical direction can be adjusted easily and accurately without mechanical adjustment. Therefore, it is possible to realize an objective lens adjusting method for an optical pickup that does not cause adjustment time loss due to mechanical adjustment and adhesion time.

[Brief description of drawings]

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

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

3A is an explanatory diagram of optical axis adjustment of an objective lens of an optical pickup of an optical disc apparatus according to an embodiment of the present invention. FIG. 3B is an optical axis of an objective lens of an optical pickup of an optical disc apparatus according to an embodiment of the present invention. Illustration of adjustment

4A 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. 4B is an optical axis of an objective lens of an optical pickup of an optical disc device according to one embodiment of the present invention. Illustration of adjustment

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 20a, 20b Focusing Coil 20c Bias Coil 21a, 21b, 21c Yoke 22a, 22b, 22c Permanent Magnet 23a, 23b, 23c, 23d Operational Amplifier VRm, VRn Half Fixed Resistance

Claims (1)

[Claims] 1. An optical pickup for an optical disk device comprising an objective lens and a lens holder which holds the objective lens and is supported so as to be finely movable in the optical axis direction of the objective lens and in the radial direction of the optical disk. A focusing coil for separately driving both ends of the lens holder in the optical axis direction of the objective lens, a tracking coil for driving in a direction orthogonal to the optical axis direction of the objective lens, and an optical disk track A bias coil for adjusting the optical axis in the vertical direction, a permanent magnet that forms a magnetic field that crosses the focusing coil, the tracking coil, and the bias coil, a yoke, and a drive for driving the focusing coil separately. Two driving circuits that generate force, and a driving force for driving the tracking coil A driving circuit for generating the bias coil, a bias current generating circuit for generating a driving force for driving the bias coil, and a bias current generating circuit for at least one of the driving circuits for the focusing coil, and the optical axis of the objective lens. A bias current is made to flow from the bias current generating circuit so that the track tangent line and the vertical direction are perpendicular to the surface of the optical disc on which the objective lens is forcibly displaceable. Optical pickup.