JPH0540950A - Focus position tracking method and device - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to a focus position tracking method and device, and more particularly, by swinging a prism provided in front of an objective lens to adjust the focus position of light from the objective lens. It is characterized in that it can move in a direction perpendicular to the optical axis of the objective lens. A focus position tracking method and apparatus according to the present invention is
The laser beam (2) from the laser light source (1) is passed through the objective lens.
In a focus position tracking method and device for focusing on a disk (5) via (4), a prism (2) that can slide the laser beam (2) before entering the objective lens (4) is used. 10), the focusing position of the laser beam (2) from the objective lens (4) through the prism (10) in the direction perpendicular to the objective lens optical axis (4a) of the objective lens (4). The configuration is such that it is moved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus position tracking method and apparatus, and more particularly, to a focus position of light from an objective lens by swinging a prism provided in front of the objective lens. The present invention relates to a new improvement for enabling movement in a direction perpendicular to the optical axis.

[0002]

2. Description of the Related Art There are various types of focus position tracking devices that have been used in the past, and a typical one will be described below. The structure generally adopted in the optical pickup shown in FIG. be able to. That is, in FIG. 4, reference numeral 1 denotes a laser light source, and the laser light flux 2 that has passed from the laser light source 1 through the collimating lens 1A is changed in direction by 90 degrees through the beam splitter 3 and then the objective lens. The optical disc 5 such as an optical disc is configured to have a focal point 6 through the optical disc 4.

Further, an actuator 7 composed of a step motor or the like is connected to the objective lens 4 via a connecting member 8. By the operation of the actuator 7,
The objective lens 4 is constructed so that it can move to the positions indicated by the solid and dotted lines.

Therefore, in the above-mentioned structure, by operating the actuator 7 to change the position of the objective lens 4, the focal point 6 of the laser beam 2 with respect to the disk 5 can be changed to achieve tracking.

[0005]

Since the conventional focus position tracking method and apparatus are configured as described above, the following problems exist. That is, since the objective lens itself is moved in the direction perpendicular to the objective lens optical axis by the actuator, the objective lens optical axis of the objective lens tilts during this movement, making it very difficult to read accurate information.

The present invention has been made in order to solve the above problems, and in particular, by swinging a prism provided in front of the objective lens, the light collecting position of the light from the objective lens is increased. It is an object of the present invention to provide a focus position tracking method and device capable of moving the lens in a direction perpendicular to the optical axis of the objective lens.

[0007]

A focal position tracking method according to the present invention is a focal position tracking method in which a laser beam from a laser light source is focused on a disk through an objective lens. The laser light beam before shining is passed through a swingable prism, and the focus position of the laser light beam from the objective lens is moved through the prism in a direction perpendicular to the optical axis of the objective lens of the objective lens. That's how it was done.

More specifically, it is a method of tilting the prism optical axis of the prism.

A focus position tracking device according to the present invention is a focus position tracking device in which a laser beam from a laser light source is focused on a disk through an objective lens, and a prism provided in front of the objective lens. And an actuator connected to the prism for swinging the prism.

More specifically, a beam splitter for refracting the laser beam is provided between the prism and the laser light source.

[0011]

In the focus position tracking method and apparatus according to the present invention, the condensing position of the light from the objective lens is made perpendicular to the objective lens optical axis by inclining the prism optical axis provided in front of the objective lens. Can be moved,
As a result, the focal position of the laser light flux with respect to the disc can be moved, and tracking adjustment can be achieved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a focus position tracking method and apparatus according to the present invention will be described in detail below with reference to the drawings.
The same or equivalent parts as those of the conventional example will be described using the same reference numerals. 1 to 3 show a focus position tracking method and device according to the present invention. FIG. 1 is a schematic configuration diagram showing the overall configuration, and FIGS. 2 and 3 are configuration diagrams showing a state where a focus position is shifted. ..

Reference numeral 1 in FIG. 1 denotes a laser light source, and a laser beam 2 passing from the laser light source 1 through a collimating lens 1A is changed in direction by 90 degrees through a beam splitter 3 and is not shown. A focus 6 is formed on a disk 5 such as an optical disk through an objective lens 4 fixedly arranged on the main body.

The objective lens 4 and the beam splitter 3
The prism 10 is provided between the objective lens 4 and the objective lens 4, and the prism 10 is connected to the connecting means 11a of the actuator 11 including a step motor or the like so that the prism 10 is connected via the actuator 11. 10 is configured to be swingable in the direction of arrow A.

Next, in the above configuration, the prism 10
A case will be described in which the focal point 6 of the disk 5 is changed by swinging. First, as shown in FIG. 2, when the focus position is shifted by −δ in the X direction with respect to the optical axis of the laser beam 2, the prism optical axis of the prism 10 is shifted by −θ via the actuator 11, A shift of −δ can be performed.

Further, as shown in FIG.
When the focal position is shifted by + δ in the X direction with respect to the optical axis of, the prism optical axis of the prism 10 is displaced by + θ via the actuator 11 so that + δ can be moved.

That is, when the prism 10 constructed such that the entrance surface and the exit surface are at β degrees is rotated by an angle of θ, the objective lens 4 is moved to the entrance axis of the objective lens 4.

[Equation 1] The laser light beam 2 inclined by the angle of the equation (1) enters. According to this inclination, the light emitted from the objective lens 4 can be condensed at a position deviated from the focal position on the optical axis to form the focal point 6, so that tracking can be achieved.

Therefore, by changing the angle of the prism optical axis of the prism (10), the focus position of the laser light from the objective lens 4 (the position where + δ or −δ is moved in FIGS. 2 and 3) is set. The objective lens 4 can be moved in a direction perpendicular to the objective lens optical axis 4a, and the focus position 6 on the disk 5 can be displaced.

[0019]

Since the focus position tracking method and apparatus according to the present invention are configured as described above, the following effects can be obtained. That is, since the prism optical axis of the prism provided in front of the objective lens can be adjusted by the actuator to move the focal point, the optical axis of the objective lens optical axis generated by moving the objective lens can be changed as in the conventional case. It is possible to achieve highly accurate tracking extremely easily without causing an error.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a focus position tracking device according to the present invention.

FIG. 2 is a configuration diagram showing a state in which the focus of FIG. 1 is shifted.

FIG. 3 is a configuration diagram showing a state in which the focus of FIG. 1 is shifted.

FIG. 4 is a configuration diagram showing a conventional focus position tracking device.

[Explanation of symbols]

 1 Laser Light Source 2 Laser Beam 3 Beam Splitter 4 Objective Lens 4a Objective Lens Optical Axis 5 Disk 6 Focus 10 Prism 11 Actuator

Claims (4)

[Claims] 1. A laser luminous flux (2) from a laser light source (1)
In the focus position tracking method in which the focus (6) is formed on the disk (5) through the objective lens (4), the laser beam (2) before entering the objective lens (4) is swayed. The objective lens optical axis of the objective lens (4) is passed through the movable prism (10), and the focusing position of the laser beam (2) from the objective lens (4) is passed through the prism (10). (4a) A focus position tracking method characterized by moving in a direction perpendicular to that. 2. The focus position tracking method according to claim 1, wherein the prism optical axis of the prism (10) is tilted. 3. A laser beam (2) from a laser light source (1)
In a focus position tracking device in which the focus (6) is formed on the disk (5) through the objective lens (4), a prism (10) provided in front of the objective lens (4), and A focus position tracking device comprising: an actuator (11) connected to the prism (10) for swinging the prism (10). 4. The prism (10) and the laser light source
The focus position tracking device according to claim 3, wherein a beam splitter (3) for refracting the laser beam (2) is provided between the focus position tracking device and the focal point tracking device (1).