JPS59178632A - Object lens supporting device for optical disc pickup - Google Patents

Abstract

PURPOSE:To shorten the length between an object lens and the end of the supporting side to enhance the stiffness in the radial direction by bending plural flat springs, each pair of which are parallel with each other, connected to a movable part and a fixed part in opposite directions and moving the object lens in parallel. CONSTITUTION:Flat springs 1a have one ends fixed to a fixed part 2 and have the other ends connected to a flat spring 1b through a connecting member 5. The flat spring 1b is placed in parallel between two flat springs 1a and is connected to a movable part lens frame 3. These flat springs are bent in opposite directions to move an object lens 4 in parallel. Consequently, the length between the object lens and the end part of a suspension is shortened by bending to enhance the stiffness in the radial direction in comparison with that in the focus direction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field to which the Invention Pertains] The present invention relates to a focus drive mechanism for an optical pickup that detects signals from an optical disc used in a digital audio player or the like.

[Prior art and its problems] An optical pickup used in a digital audio player generally has a mechanism for driving an objective lens in the optical axis direction. This mechanism moves the objective lens in parallel within a range of about ±1 mm, and one conventional optical pickup uses a diaphragm spring to support the objective lens, as shown in Figure 1. be. The leaf spring 1 extends radially from the lens frame 3 in an arc with the objective lens 4 at its center, and is joined by a fixing part 2. When the objective lens 4 moves in a direction perpendicular to the plane of the drawing in FIG. 1, the leaf spring 1 is not only bent but also slightly twisted. Further, the objective lens 4 undergoes some rotation.

Since the leaf spring is forced to undergo complex deformation in this way, the overall strength of the spring in the focus direction becomes large.If the objective lens driving range is widened, the diameter of the diaphragm spring becomes large, and the lens 4 The distance from the center of the support section to the side edge of the support section becomes longer. This is undesirable because it limits the size of the motor used in the player's optical disc rotation drive system.

The objective lens of an optical pickup needs to be radially driven not only in the focus direction but also in a direction perpendicular to it, and some lenses are driven together with this diaphragm spring. In this case, when the leaf spring 1 is driven in the radial direction while being displaced in the focus direction with the structure shown in FIG. Due to the complexity of deformation in the focus direction, the rigidity of the pillow in the radial direction becomes weak. A fatal sub-resonance appears in the radial vibration characteristics of this useless pickup.

[Objective of the Invention] This invention was made based on the above circumstances, and it reduces the distance from the center of the objective lens to the side edge of the suspension mechanism, and increases the rigidity in the radial direction compared to the rigidity in the focus direction. The purpose of this invention is to develop a focus suspension mechanism for an optical pickup.

[Summary of the Invention] When attempting to realize parallel motion by bending a leaf spring, in addition to the intended movement direction of the movable part, there is some movement in the plane direction of the leaf spring in a direction perpendicular thereto. For this reason, springs whose periphery is fixed, such as diaphragm springs, have a structure that absorbs this through rotation of the objective lens, etc., but in the present invention, multiple leaf springs are folded back in series in opposite directions, and the leaves of each spring are used. It has a structure that absorbs the displacement of the spring in the plane direction. The structure is such that the inertial force of the movable rate against the drive in the radial direction is mainly received only by the shear force of the leaf spring. In order to regulate the tilt of the objective lens, the objective lens is stacked in two stages in the optical axis direction, and the folded parts of the upper and lower leaf springs are connected so that the deformation of the upper and lower leaf springs is always the same. do. This mechanism is constructed in a symmetrical shape around the lens.

[Effects of the Invention] By adopting the structure described above, compared to a conventional diaphragm spring having the same rigidity as a suspension, it is possible to reduce the size by folding back the leaf spring. In particular, this structure is advantageous in shortening the distance from the center of the objective lens to the end surface of the suspension.

Focus suspension is also radial drive k) Jf
In the optical peak-up method, the rigidity in the radial direction of the suspension W/ is expected only from the shear force of the leaf spring, so the leaf spring is deformed depending on which position in the focus direction the objective lens moves. However, the rigidity is almost the same.

Examples of the invention] Examples are shown in FIGS. 2 and 3.

One end of the leaf spring 1a is fixed to the fixing part 2, and the other end is joined to the leaf spring lb by a connecting member 5. Leaf spring lb is 2
It is located in parallel between the two leaf springs 1a and is joined to the movable lens frame 3. The length direction of the leaf springs la, lb and the direction perpendicular to the optical axis of the objective lens 4 are the radial direction of the pickup, and the leaf springs la, lb are symmetrical with the radial direction passing through the center of the objective lens 4 as an axis. Placed.

The suspension shown in FIG. 2 is arranged above and below, as shown in FIG. 3, and connects the tips of the leaf springs with a connecting member 5.

The distance from the objective lens 4 to the side edge of the suspension is equal to the width of the leaf spring 1a.

This length can be determined independently of the stiffness of the spring in the focus direction of the objective lens 4.

In addition, the rigidity of the objective lens 4 in the focus direction is determined by the free end of the connecting member 5 where the leaf spring is at its tip, so when it is displaced in the focus direction, there is no expansion or contraction of the leaf spring and the rigidity in the focus direction is Does not contribute to stiffness. Only the bends with fixed ends are stiff and determine the spring constant of the suspension.

In this case, the distance from the center of the objective lens 4 can be reduced also in the length direction of the barbs Ia and lb compared to a diaphragm spring which is fixed at one periphery and has the same rigidity and the same drive range.

As described above, compared to the conventional diaphragm spring, the spring can be made smaller in any direction around the objective lens 4. In terms of radial rigidity, the bridge is supported by the shear force of almost all the leaf springs that make up the suspension, making it stronger than conventional ones.

[Other Embodiments of the Invention] In the embodiment shown in FIG. 2, two parallel leaf springs connected to the movable part and the fixed part are arranged in the same plane.
As shown in the figure, a two-layer structure may be used instead of folding the leaf springs in the same plane. By doing so, the distance between the center of the objective lens 4 and the 1111 point can be further shortened.

Further, the shape of the leaf spring does not necessarily have to be rectangular and have a uniform thickness.In consideration of bending deformation of the leaf spring, it is also possible to make the shape of the middle part of the leaf spring larger in width and thickness. By doing so, the rigidity of the suspension in the radial direction can be further increased.

[Brief explanation of drawings]

FIG. 1 is a conventional example, FIG. 2 is an embodiment of the present invention, FIG. 3 is a perspective view of the embodiment of the present invention, and FIG. 4 is a perspective view of another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Leaf spring, 1a... Leaf spring joined to the fixed part, 1b...=R Leaf spring joined to the moving part, 2... Fixed part, 3... Lens frame, 4 ...objective lens,
5...Connection member. Agent: Patent attorney Kensuke Chika (and 1 other person)

Claims (1)

[Claims] One end of a plurality of parallel leaf springs is joined, an end opposite to at least one leaf spring joint of the plurality of leaf springs is joined to a movable part including an objective lens, and a leaf spring joint of the remaining leaf springs is joined. The opposite end of the leaf springs is joined to the fixing part, and the bending direction of the plurality of leaf springs is made to match the optical axis direction of the objective lens, and the tension and compression direction is made to match the rotational circumferential direction of the optical disk. An objective lens support device for an optical disk pickup, characterized in that a movable part including the objective lens is moved in parallel by arranging a plurality of elements, each of which is a leaf spring element, at least in the optical axis direction of the objective lens.