JPH0636498Y2 - Optical pickup - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical pickup used for optically reading recorded information in a video disc player or the like.

The optical pickup is used, for example, in a video disc player to optically read recorded information, and is configured to perform focus adjustment and tracking adjustment.

1 (a) to 1 (c) are a plan view XX sectional view and an YY sectional view showing an example of an optical pickup generally used in the past. In the figure, reference numeral 1 is an objective lens provided at the tip of the lens barrel 2, and 3 is a bobbin, one end of which is fixed to the lens barrel 2. Reference numeral 4 is a pole, 5 is a magnet, and 6 is a yoke, which constitute a magnetic circuit sandwiching the inner and outer surfaces of the bobbin 3, and the bobbin 3 is housed in the void portion of the magnetic circuit. Reference numeral 7 is a focusing coil wound around the bobbin 3, and 8 is a tracking coil wound around the axis of the bobbin 3 by being divided into two parts. The relationship between the bobbin 3, the focusing coil 7 and the tracking coil 8 in this case is that the focusing coil 7 and the tracking coil 8 are parallel to the magnetic path facing surface as shown in the perspective view of FIG. It is wound in the installed state.

The optical pickup thus constructed is normally held in a neutral state by a damper (not shown) as shown in FIG. 3 (a). Then, in this state, when a current in the illustrated direction is passed through the tracking coil 8, the tracking coil 8 produces a horizontal force orthogonal to the axis due to the interaction with the magnetic flux generated in the air gap of the magnetic circuit. Upon receipt, the driven part including the objective lens 1 and the lens barrel 2 is moved to perform tracking adjustment. In this case, since the upper and lower tracking coils 8 generate magnetic fluxes having opposite polarities, even if some magnetic flux leakage occurs, they cancel each other out and do not affect other parts. . Further, since the center of gravity 9 of the driven portion coincides with the driving point 10, the rolling action does not occur in this state.

Next, when a current is passed through the focusing coil 7, a force is applied in the void portion of the magnetic circuit to move the driven portion in the focus direction as shown in FIG. 3 (b) to perform focus adjustment. .

However, in the optical pickup having the above-described structure, the center of gravity 9 of the driven part moves in the focusing direction during focusing adjustment, so that its center of gravity 9 moves as shown in FIG. Misalignment occurs between them.
As a result, a torque is generated around the center of gravity 9 of the driven portion. Further, since a part of the tracking coil 8 is separated from the effective portion of the magnetic gap and protrudes to the outside, an imbalance occurs between the upper and lower forces. That is, in such a configuration, when the offset is made in the focusing direction, a torque around the center of gravity is generated in the driven portion,
Along with this, not only the driven part rolls and tilts, but also a part of the tracking coil 8 is located outside the effective magnetic flux of the magnetic circuit, so a sufficient driving force cannot be obtained, This causes a problem that the sensitivity is lowered, which is a fatal problem for the optical pickup.

Therefore, an object of the present invention is to provide an optical pickup that does not tilt even when it is offset in the focus direction.

In order to achieve such an object, the present invention is such that the tracking coil is always placed in the air gap of the magnetic circuit. Hereinafter, the optical pickup according to the present invention will be described in detail with reference to the drawings.

FIG. 4 is a sectional view of an essential part showing an embodiment of the optical pickup according to the present invention, and the same parts as those in FIG. 1 are indicated by the same symbols. In the figure, 11 is a tracking coil. In this case, the upper and lower coils are wound on the focusing coil 7 as shown in FIG. 6, and the mutual distance between them is the axis in the air gap of the magnetic circuit. It is made sufficiently smaller than the dimension in the direction.

In the optical pickup thus constructed, when a current is supplied to the focusing coil 7, the driven portion moves in the focusing direction as shown in FIG. 5 as in the case described above. However, in this case, the vertical dimension of the tracking adjustment coil 11 is made sufficiently smaller than the corresponding dimension of the air gap. Therefore, even when the tracking coil 11 is offset in the focus direction, the tracking coil 11 is always located in the effective portion of the void portion. As a result, the magnetic flux with respect to the tracking coil 11 is always uniform, and even if the driven portion is offset in the focusing direction as shown in FIG. 5, the driving point and the center of gravity coincide. Further, the imbalance between the upper and lower portions of the tracking coil 11 and the left and right forces is canceled and does not occur, so that the occurrence of rolling is reliably prevented.

In addition, in the above-mentioned embodiment, only the case where the rectangular bobbin is applied has been described, but the bobbin may have any shape.

As described above, the optical pickup according to the present invention is configured such that the tracking control coil is always positioned in the air gap of the magnetic circuit. Accordingly, there is an excellent effect that stable optical reading can be performed along with this, and a decrease in sensitivity when offset in the focus direction can be prevented.

[Brief description of drawings]

1 (a) to 1 (c) are a plan view and a side view of essential parts showing an embodiment of a conventional optical pickup, and FIG. 2 is a perspective view of a driven part in FIG. 1, and FIG. (A) and (b) are sectional views showing the operation of the optical pickup shown in FIG. 1, FIG. 4 is a sectional view showing the operation of the optical pickup according to the present invention, and FIG. FIG. 6 is a cross-sectional view of a main part showing a state during focus adjustment, and FIG. 6 is a perspective view of a driven part. 1 ... Objective lens, 2 ... Lens barrel, 3 ... Bobbin, 4 ...
Pole, 5 ... Magnet, 6 ... Yoke, 7 ... Focusing coil, 11 ... Tracking coil.

Front page continuation (72) Inventor Yasuko Wada, 426-10 Hanazono, Tokorozawa, Saitama Prefecture, Tokorozawa Plant, Pioneer Co., Ltd. (72) Ikuya Kikuchi 4-2610 Hanazono, Tokorozawa, Saitama Prefecture, Tokorozawa Plant, Pioneer Co., Ltd. (56) Reference JP-A-54-94007 (JP, A) JP-A-57-71530 (JP, A) JP-A-57-8928 (JP, A)

Claims (1)

[Scope of utility model registration request] 1. A driven part having an optical system including an objective lens, and driving means for driving the driven part in an optical axis direction and a direction orthogonal to the optical axis, wherein the driving means has a coil center portion. A first coil wound in parallel with the optical axis direction;
The coil axis is wound on the first coil in the direction of the center of gravity of the driven portion in a direction orthogonal to the optical axis direction, and the length of the coil side in the optical axis direction is the above. A plurality of second coils narrower than the winding width of the first coil;
An effective magnetic flux of the magnetic circuit is formed by a magnetic circuit that generates a magnetic flux interlinking with the first coil and the second coil, and the second coil is within a drive range of the driven unit in the optical axis direction. An optical pickup that is configured to fit inside.