KR20030012677A - The method for the expansion of focal length - Google Patents

Abstract

PURPOSE: A technique of extending a focal distance is provided to drive a very small-sized lens finely to enable focus control in a wide range and miniaturize an optical pick-up head for use in a CD or DVD. CONSTITUTION: The distance between a convex lens(1) and a concave lens(2) is controlled to adjust a focus(4) on which parallel beams are focused. The concave lens is placed in the focus(3) of the convex lens while the convex lens being fixed, and the concave lens is moved finely, to largely move the focus on which the parallel beams are focused.

Description

Focal Length Expansion Technique {The method for the expansion of focal length}

In the optical pickup element of a CD or DVD currently used, a moving coil is driven by a voice coil driver to control the focus position of the laser light. If the convex lens and the voice coil driver are miniaturized to reduce the weight of the optical pickup head and increase the response speed, the focusing range is reduced, so that it is impossible to adjust the focus in response to the vibration of the disk surface.

The present invention relates to a technique that can be adjusted by extending the focal length of the micro optical pickup element. Research into miniaturizing pickup elements such as CDs and DVDs, which are widely used at present, is being conducted. If the driver is miniaturized with the lens, the driving range of the lens becomes smaller, and thus focusing is impossible. Thus, there is a need for a new focusing technique that can achieve a large focusing range with a small operating range.

1 is a conceptual diagram of a focal length extension adjustment technique according to the present invention;

-Explanation of symbols for the main parts of the drawings-

One ; convex

2 ; Concave lens

3; Where images form when there is no concave lens

4 ; Image forming position when there is concave lens

5; Distance between the position of the focal point of the convex lens and the concave lens

6; Distance between the focus position of the convex lens and the focus position changed by the concave lens

The present invention relates to a technique that can be adjusted by extending the focal length of the micro optical pickup element. 1 is a conceptual diagram for expanding and adjusting a focal length in the present invention. The focus is adjusted using convex and concave lenses. Even the minute movement of the concave lens or the convex lens can greatly change the position where the image is formed.

In the present invention, the distance 4 between the convex lens 1 and the concave lens 2 is adjusted to adjust the position 4 at which the image of parallel light is formed. In FIG. 1, when the convex lens 1 is fixed, the concave lens 2 is positioned in the focal point 3 of the convex lens and the position of the concave lens is moved finely. . For example, when using a concave lens having a focal length of 100 μm, changing the distance 5 between the focus position 3 of the convex lens and the concave lens 2 from 90 μm to 95 μm results in no concave lens. The distance 6 between the image forming position 3 and the image forming position 4 when the concave lens is present varies from 0.8 mm to 1.8 mm. The change in the position at which the image is condensed compared to the position shifting distance of 5 mu m of the concave lens is 1 mm, and a 200 times focal length amplification effect is obtained. In this way, instead of fixing the convex lens and moving the concave lens, the same effect as described above is obtained even when the concave lens is fixed and the convex lens is moved.

Since the invented focal length extension adjustment technique enables the micro lens to be driven finely to enable a large range of focus adjustment, this method is suitable for the dynamic focus adjustment required for the optical pickup element. In addition, the micro lens can be minutely driven using a micro driver, and the optical pickup head used in a CD or a DVD can be miniaturized by integrating a micro lens and a micro driver using micromachining technology.

Claims (3)

Focal Length Expansion Technique Using Convex and Concave Lenses. Technique to fix the convex lens and finely move the concave lens to obtain the amplification effect of focal length Technique for fixing concave lenses and finely moving convex lenses to achieve amplification of the focal length.