JP2827004B2 - Pickup device in optical information reader - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pickup device in an optical information reading device. 2. Description of the Related Art In an optical information reading apparatus, a disk such as a video disk or a digital audio disk as an information recording medium has fine pits (dents) corresponding to information signals on its surface in a spiral track. The information signal is recorded by forming as. When reproducing such a disc, the disc is irradiated with spot light while rotating the disc at a predetermined number of revolutions, and a change in the intensity of the reflected light or transmitted light is converted into an electric signal, which is used as an original information signal. It is something to play. In the reproduction of the disk, the irradiation light must be accurately focused on the recording surface of the disk. Therefore, the position control (focus servo) in the direction perpendicular to the recording surface of the optical system, that is, in the focus direction, is required. In addition, the irradiation light must always accurately follow the recording track, and therefore, it is necessary to control the irradiation light in the radial direction of the disk, that is, in the tracking direction (tracking servo). For this purpose, in a reading pickup device in an optical information reading device, a support mechanism for movably supporting an optical system for irradiating a spot light for reading information on a disk recording surface in a focusing direction and a tracking direction, a focusing error, And a driving device for driving the optical system in the focusing direction and the tracking direction according to the signal and the tracking error signal. [0005] Various such pickup devices have been proposed in the past, one example of which is shown in FIG. As shown, an optical system 4 having an objective lens 2 and a cylindrical portion 3 is fixed to a free end of a cantilever-like member 1 having one end fixed. The cantilever-shaped member 1 is disposed in parallel with a disk recording surface (not shown), and has a leaf spring portion 5 that is flexible only in the optical axis direction of the optical system 4, that is, in the focus direction Z. And a leaf spring portion 6 that is flexible only in a tracking direction X perpendicular to the tracking direction. A driving coil 8 in the focus direction Z is wound around a circular bobbin 7 fixed below the cylindrical portion 3, and a pair of bobbins 9 provided on the cylindrical portion 3 so as to protrude in the tracking direction X. Has the tracking direction X
The driving coil 10 is wound. Further, a magnetic circuit (not shown) for applying an electromagnetic driving force to each of the driving coils 8 and 10 is provided. When an appropriate current is supplied to the driving coils 8 and 10, the leaf springs 5 and 6 bend in the focusing direction Z and the tracking direction X, respectively, and the optical system 4 is driven. In a conventional pickup device of an optical information reading apparatus, a support mechanism of an optical system has two degrees of freedom in only one of a focus direction and a tracking direction. It is configured by a combination of support mechanisms. Therefore, the structure was complicated, and it was difficult to manufacture. In addition, since the two support mechanisms are combined, there are disadvantages that a large volume is required, miniaturization is difficult to achieve, and parasitic resonance easily occurs. The present invention has been made in view of the above points, and an object of the present invention is to provide a pickup device which has a simple structure, is easily miniaturized, is inexpensive, and operates stably. is there. A pickup device of an optical information reading apparatus according to the present invention comprises an objective lens for irradiating light onto a recording surface of a recording medium, and an objective lens for holding the objective lens. A holding member, driving means for driving the objective lens in two directions, that is, an optical axis direction of the objective lens and a direction perpendicular to the optical axis direction, and a support mechanism for supporting the objective lens movably in the two directions. Wherein the support mechanism extends substantially perpendicularly to the two directions, is flexible in any of the two directions, and has a free end coupled to the objective lens holding member. And the line connecting the four points, which are the connection points of the elongated flexible member and the objective lens holding member, forms a quadrilateral. It is characterized in that a flexible member is arranged. According to the present invention, the support mechanism of the holding member of the pickup device of the optical information reading device extends in two directions perpendicular to the optical axis direction and the direction perpendicular to the optical axis direction. Since four cantilever-shaped elongated flexible members are used, a single support mechanism can be configured to have a degree of freedom in the above two directions, so that the support mechanism can be downsized compared to the related art. it can. Hereinafter, a pickup device according to the present invention will be described with reference to the accompanying drawings. As shown in FIGS. 1 and 2, a driving coil 13 in the optical axis direction of the optical system 11, that is, in the focus direction Z is provided on the outer periphery of the circular bobbin portion 12 provided in the optical system 11 in the circumferential direction. It is wound. A pair of substantially rectangular bobbin parts 15 and 16 are provided on the cylindrical part 14 of the optical system 11 so as to protrude in a direction perpendicular to the optical axis direction, that is, in the tracking direction X.
The bobbins 15 and 16 each have a tracking direction X.
Are wound around the driving coils 17 and 18. Reference numeral 19 denotes an objective lens fitted in the cylindrical portion 14 and constitutes a part of the optical system together with the cylindrical portion 14. On the upper and lower surfaces of the fixed portion 20, four grooves 21 are provided at right angles to the focus direction Z and the tracking direction X, each of which is two in total. One end of each of the four longitudinal flexible members 22 is fitted into the four grooves, and is fixed with an adhesive or the like. The flexible members 22 are made of, for example, beryllium copper or the like, and are formed so that four of them have substantially the same length and a cross section perpendicular to the longitudinal direction is rectangular. As described above, each free end of the flexible member 22 fixed in a cantilever shape to the fixing portion 20 is connected to the outer peripheral surface of the cylindrical portion 14 by the connecting member 23, The flexible members 22 are arranged so that they are substantially parallel and their cross-sections face the same direction. As is clear from FIG. 2, a line connecting the four points, which are the connection points of the flexible member 22 and the cylindrical portion 14, forms a quadrilateral, and a pair of connection points located on the diagonal of the quadrilateral. Are positioned so that the straight line AA and the straight line BB connecting the two pass through the center of gravity (point G) of the optical system 11. Each of the driving coils 1
A magnetic circuit (not shown) for applying an electromagnetic driving force to each of the driving coils corresponding to 3, 17 and 18
Is provided. During the reading operation of the pickup device, when an appropriate current is supplied to each of the driving coils 13, 17, and 18, the flexible member 22 flexes in the focus direction Z and the tracking direction X as needed, causing the optical system 11 to flex. It is driven in both directions. . Here, as described above, the line connecting the four points, which are the connection points of the flexible member 22 and the cylindrical portion 14, forms a quadrilateral, and is a set of diagonally opposite sides of the quadrilateral. By making the straight line connecting the coupling points pass through the center of gravity of the optical system 11, the optical system 11 is driven in parallel to the tracking direction X or the focus direction Z without rotating. The cross-sectional shape of the flexible member 22 is not limited to the rectangular shape as described above, but may be, for example, a circular shape or a square shape. However, by making the cross-sectional shape rectangular, the cross-sectional dimensions in the focus direction Z and the tracking direction X are changed, and the bending rigidity of the flexible member 22 in each of the above directions can be appropriately determined. 2
The low-band resonance frequency in each of the two directions can be any convenient frequency. If the cross-sectional areas are the same, the torsional rigidity can be maximized by making the cross-sectional shape rectangular. On the other hand, when the cross section is circular or square, there is no directionality of the cross sectional shape, so that it is possible to form, for example, only by cutting a commercially available wire into an appropriate length, thereby simplifying the assembling work and Costs can be reduced. As described above in detail, in the pickup device of the optical information reading apparatus according to the present invention, the support mechanism for supporting the objective lens is provided in a direction perpendicular to the optical axis direction of the objective lens and the optical axis direction. Four cantilever beams that extend substantially perpendicular to the two directions and are flexible in any of the two directions and have their free ends coupled to an objective lens holding member that holds the objective lens. It is composed of an elongated flexible member. Therefore, a single supporting mechanism can be configured to have a degree of freedom in the two directions, and the supporting mechanism can be downsized as compared with a conventional pickup device. In addition, 4
The optical system is arranged by arranging the elongated flexible member such that a line connecting four points, which are the connecting points between the cantilever elongated flexible member and the objective lens holding member, forms a quadrilateral. 11
Is driven in parallel to the tracking direction X or the focus direction Z without rotating, and a stable operation can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a pickup device of an optical information reading device according to the present invention. FIG. 2 is a cross-sectional view of a pickup device of the optical information reading device according to the present invention. FIG. 2 is a diagram showing a pickup device of the optical information reading device of FIG. [Description of Signs] 11 Optical systems 12, 15, 16 Bobbin portions 13, 17, 18 Driving coil 14 Cylindrical portion 19 Objective lens 20 Fixed portion 22 Flexible member

Claims (1)

(57) [Claims] An objective lens for irradiating light onto the recording surface of the recording medium, an objective lens holding member for holding the objective lens, and the objective lens in an optical axis direction of the objective lens and a direction perpendicular to the optical axis direction. A pickup device comprising: a driving unit that drives in two directions; and a support mechanism that movably supports the objective lens in the two directions, wherein the support mechanism extends substantially perpendicular to the two directions, and It comprises four cantilevered elongated flexible members which are flexible in any of two directions and whose free ends are connected to the objective lens holding member, wherein the elongated flexible member and the objective lens holding member are provided. A pickup device in an optical information reading device, wherein the elongated flexible member is arranged so that a line connecting four points that are connection points with a member forms a quadrilateral.