JP2001134975A - Objective lens for optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an objective lens with which the sticking of the objective lens to an objective lens fixing holder to regulate the comatic aberration and tilt of the lens or the regulating of the optical axis tilt of the laser beam of an optical pickup device may be inexpensively and rapidly realized by an autocollimator, etc. SOLUTION: A mirror finished surface flat surface 13a which is a reference plane to assure the perpendicularity with high accuracy to the optical axis 11 of the objective lens 1 is formed on the outer peripheral part of an upper aspherical surface 13 at a width, at which the reflected light from this mirror finished surface flat surface may be easily obtained, when the flat surface is irradiated with parallel light beams, by which the sticking of the objective lens to the objective lens fixing holder to regulate the comatic aberration and tilt of the lens or the regulating of the optical axis tilt of the laser beam of the optical pickup device with the autocollimator may be easily and rapidly realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens for an optical disk used in an optical pickup device or the like which is capable of reading or writing a DVD disk or a CD disk or both functions.

[0002]

2. Description of the Related Art In an optical pickup apparatus for reading or writing a DVD disk or a CD disk, or for supporting both functions, an objective lens coma aberration tilt adjustment bonding method to an objective lens fixing holder, or an optical axis tilt adjustment of the optical pickup apparatus. As a method, a tilt adjustment method for measuring an optical spot of a laser beam condensed by an objective lens or an observation adjustment method for measuring characteristics such as an output waveform of an optical pickup device and a jitter value is generally used.

The above-mentioned methods require submicron focusing, high-precision image processing technology for the primary light of a converging spot, and high-precision skill adjustment technology for observing the characteristics of an optical pickup device. And it is expensive equipment.

[0004]

Therefore, it is desired that the adjustment of the tilt of the coma aberration of the objective lens to the holder for fixing the objective lens or the tilt adjustment of the optical axis of the laser of the optical pickup device can be realized at a low cost and in a short time by an autocollimator or the like. ing. However, this cannot be achieved with the conventional optical disk objective lens.

FIG. 5 is a view showing the shape of an objective lens according to a conventional example. The conventional objective lens 1 has a structure or quality in which there is no portion serving as a high-precision perpendicular reference plane with respect to the optical axis 11 or there is no guarantee of accuracy as a high-precision perpendicular reference plane with respect to the optical axis. Reference numeral 12 in the drawing denotes an optical axis reference plane.

An object of the present invention is to provide an objective lens in which the adjustment of the tilt of the coma aberration of the objective lens to the holder for fixing the objective lens or the tilt adjustment of the optical axis of the laser of the optical pickup device can be performed at low cost and in a short time by an autocollimator or the like. With the goal.

[0007]

In order to achieve the above object, a first means is to provide an objective lens for an optical disk used in an optical pickup device compatible with reading or writing of a DVD disk or a CD disk or both functions. A flat mirror surface is formed on the outer peripheral portion of the upper aspherical surface, which is a reference surface for guaranteeing a right angle with high accuracy to the optical axis of the objective lens.

[0008] The second means is the first means,
The flat mirror surface is formed to have such a width that the reflected light of the flat mirror surface can be easily obtained when the parallel light is irradiated.

In the present invention, on the outer peripheral portion of the upper aspherical surface,
The mirror flat surface, which is a reference plane that guarantees a high-precision right angle to the optical axis of the objective lens, is formed with a width that allows the reflected light of the flat mirror surface to be easily obtained when irradiating parallel light. The tilt adjustment of the objective lens coma aberration, or the tilt adjustment of the optical axis of the laser beam of the optical pickup device can be performed inexpensively and in a short time by an autocollimator or the like.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a shape of an objective lens for an optical disk according to an embodiment of the present invention. In the present invention, a flat mirror surface 13a is provided on the outer peripheral portion of the upper aspherical surface 13 of the objective lens 1 as a reference surface for guaranteeing a right angle with respect to the optical axis of the objective lens 1 with high accuracy. The mirror flat surface 13a is formed to have such a width that the mirror flat surface reflected light can be easily obtained when the parallel light is irradiated.

[0011] Thus, the adjustment of the tilt of the coma aberration of the objective lens to the holder for fixing the objective lens or the adjustment of the tilt of the optical axis of the laser beam of the optical pickup device can be realized at low cost and in a short time by an autocollimator or the like.

Next, the configuration of an objective lens driving device incorporating the objective lens 1 will be described. 2 to 4 show the configuration of a basic objective lens driving device.
Is a cross-sectional view of the objective lens driving device in the tangential direction of the optical disc,
FIG. 3 is a side view of the objective lens driving device, and FIG. 4 is a sectional view of the objective lens driving device in a radial direction of the optical disk.

The objective lens 1 is disposed on an upper surface of a lens holder 2, a focusing coil 3 is wound around a side surface of the lens holder 2, and a tracking coil 4 and the objective lens 1 are mounted on a side surface of the lens holder 2 in a radial direction of the optical disc. A tilting coil 9 that is driven to tilt is attached.

The four parallel linear elastic support members 8 are:
The lens holder 2 having one end fixed to the lens holder 2 and the other end fixed to the fixing portion, and supporting the objective lens 1,
It can be moved in the focusing and tracking directions,
In addition, it is elastically supported so that it can be tilted in the radial direction of the optical disc.

A magnetic circuit composed of a yoke 5 and a magnet 6 is disposed on a fixed portion to which one end of the elastic support member 8 is fixed, and a driving current flowing through the focusing coil 3, the tracking coil 4, and the tilt coil 9 is provided. Is
It is arranged to act on the magnetic flux generated from this magnetic circuit. An inclination detector 7 for detecting the inclination of the optical disk is arranged on the upper surface of the lens holder 2 supporting the objective lens 1. At the time of the focusing control, the current is appropriately supplied to the focusing coil 3 to operate the objective lens 1 in the optical axis direction in accordance with the deflection of the optical disk recording surface, and the spot of the light beam follows the optical disk recording surface. Can be done.

At the time of tracking control, an appropriate current is supplied to the tracking coil 4 in accordance with the eccentricity and meandering of the track of the optical disk, and the objective lens 1 is operated in a direction perpendicular to the optical axis to make the spot of the light beam. It can follow the track of the optical disc.

With respect to the tilt of the optical disk, an appropriate current is supplied to the tilt coil 9 based on the signal from the tilt detector 7 to drive the objective lens 1 to tilt corresponding to the tilt of the optical disk.

[0018]

According to the present invention, when a mirror flat surface serving as a reference plane for guaranteeing a right angle with high precision to the optical axis of the objective lens is irradiated on the outer peripheral portion of the upper aspheric surface in parallel light, the mirror flat surface reflected light Is formed in a width that can be easily obtained, so that it is possible to attach the objective lens coma tilt adjustment to the objective lens fixing holder or adjust the tilt of the optical axis of the optical pickup device at low cost and in a short time using an autocollimator. can do.

[Brief description of the drawings]

FIG. 1 is a diagram showing a shape of an objective lens for an optical disc according to an embodiment of the present invention.

FIG. 2 is a sectional view of an objective lens driving device in a tangential direction of an optical disk.

FIG. 3 is a side view of the objective lens driving device.

FIG. 4 is a sectional view of the objective lens driving device in a radial direction of the optical disk.

FIG. 5 is a diagram showing a shape of an objective lens according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Objective lens 2 Lens holder 3 Focusing coil 4 Tracking coil 5 Yoke 6 Magnet 7 Tilt detector 8 Elastic support member 9 Tilt coil 11 Optical axis 12 Optical axis reference plane 13 Upper aspherical surface 13a Mirror flat surface

Claims (2)

[Claims] In an objective lens for an optical disk used in an optical pickup device, a flat mirror surface is formed on an outer peripheral portion of an upper aspheric surface as a reference surface for guaranteeing a right angle with high accuracy to an optical axis of the objective lens. An objective lens for an optical disk, characterized in that: 2. An optical disk objective lens according to claim 1, wherein said flat mirror surface is formed to have such a width that said mirror flat surface reflected light can be easily obtained upon irradiation of parallel light. Objective lens.