JPH0320820B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical system drive device used for reading recorded information from, for example, a video disc, an audio disc, or the like, and conversely writing information.

In an optical video disc system, a laser beam emitted from a laser light source scans the disc surface and reads recorded information, so the disc can be used semi-permanently. For this reason, it is said to be the most excellent system, and various proposals have been made for optical system drive devices used particularly in this field. However, an optical system drive device that can perform focusing operations and tracking operations at high speed, as well as stable radial feeding, has not yet been realized.

The present invention has been made in view of the above points, and its first object is to provide an optical system drive device that is capable of high-speed focusing and tracking operations, as well as stable radial feeding, and that has a simple structure. The aim is to realize this.

A second object is to realize an optical system drive device which can have a wide tracking control range and does not require high precision in radial feeding.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a perspective view showing an embodiment of an optical system driving device according to the present invention, and this embodiment is embodied as an optical pickup device for reading recorded information from a disk. In the figure, numeral 1 denotes a main drive means, which includes a pulse motor, a torque motor, etc. 2
A main arm is rotated by the main driving means 1 on a plane substantially parallel to the disk surface, and a first optical system 3 is attached to one end. The first optical system 3, as shown in the cross section in FIG.
and a collimator lens 35, etc., and each of these components is maintained in a constant positional relationship by a case 36. Reference numeral 4 denotes a sub-arm supported by the main arm 2, and a second optical system 5 having a condensing lens 5a is attached to one end of the sub-arm so as to face the first optical system 3. . This focusing lens 5a receives the parallel light flux emitted from the first optical system 3, forms a beam spot on the disk surface (not shown), and returns the reflected beam from the disk surface to the first optical system 3. It is meant to guide you. The support of the sub arm 4 by the main arm 2 is as follows:
Specifically, this is carried out using the support body 6 made of an elastic material. Reference numeral 7 denotes a sub-driving means that drives at least the second optical system 5 in a direction perpendicular to the disk surface (the first
It can be driven in the z-direction in the figure) and can be rotated in a plane substantially parallel to the disk surface (moved in the θ direction in FIG. 1). This sub-driving means 7 is
For example, as shown in FIG. 3, a driving arm 8 is provided at the other end of the sub-arm surface 4, and movable coils 81 and 82 are provided for applying forces in the two directions described above to this arm 8.
, and a magnetic circuit (not shown) for placing the moving coils 81 and 82 in a predetermined magnetic field is attached to the other end of the main arm 2. In this way, the sub-drive means 7
This acts as a counterweight to the optical system 3 of the main arm 2, and stabilizes the operation of the main arm 2 and the stable drive of the first optical system 3.

Furthermore, in the apparatus of the present invention, as shown in FIG. 4, the second optical system 5 is rotated in a plane substantially parallel to the disk surface by the sub-drive means 7 (rotation in the θ direction in FIG. 1). The distance L ₁ between the center O ₁ and the center O ₂ of the focusing lens 5a of the second optical system 5 is the rotation center O ₁ and the center of the light beam emitted from the first optical system 3.
It is chosen to be approximately ΔL larger than the distance L ₂ from O ₃ .

Here, ΔL=L ₁ −√ ₁ ² −(2-2) ² However, D: Effective diameter d of the light beam emitted from the first optical system 3; Effective diameter of the focusing lens 5a In the above embodiment, the first The laser beam emitted from the laser diode 31 in the optical system 3 passes through the half mirror 33 and collimator lens 3 in the optical system 3.
5, the condenser lens 5 forming the second optical system 5
a and forms a beam spot on the disk surface. This beam spot is moved in the radial direction by rotating the main arm 2 with the main drive means 1. The reflected beam on the disk surface passes through the second optical system 5, returns to the first optical system 3 again, passes through the collimator lens 35, the half mirror 33, and the cylinder lens 34, and then
The light reaches the light receiving section 32. As a result, not only recorded information can be read, but also control signals for performing focusing and tracking operations can be obtained. The sub-drive means 7 receives the control signal and performs focusing by moving the second optical system 5 in the z direction in FIG.
Tracking is performed by rotating the second optical system 5 in the direction.

By the way, as a result of selecting the distances L ₁ and L ₂ as described above, during tracking, the focusing lens 5
The circle C ₁ of the effective diameter of a moves so that it is inscribed with the circle C ₂ of the effective diameter of the luminous flux emitted from the first optical diameter 3 at points P ₁ and P ₂ (both ends of the diameter) in Fig. 4. . That is,
The amount of movement of circle C ₁ within circle C ₂ is chosen to be maximum.

For this reason, the tracking control range can be made the widest (note that FIG. 4 is drawn with emphasis on important points for ease of understanding). Here, ΔL when circle C ₁ is inscribed with circle C ₂ and P ₁ and P ₂
It will be explained next that the value of is expressed by the above formula.
First, as shown in Figure 4, when circle C ₁ moves upward in Figure 4 and is inscribed in circle C ₂ at _point P, the center of circle C ₁
The position O ₂ has moved is O _2A , and when circle C ₁ moves downward in Figure 4 and is inscribed in circle C ₂ at point P ₂ , circle C ₁
If the position to which the center O ₂ of has moved is O _2B , then ΔL becomes as follows, ΔL=L ₁ −L ₂ =L ₁ − _{1 3} =L ₁ −√ _{1 2A} ² − _{3 2A} ^2Here , , _{1 2A} = L _{1 3 2A} = _{1 3} − _{1 2A} = D/2−d/2, so by substituting these, we get ΔL=L ₁ −√ ₁ ² −(2−2) ² , and the above We can obtain the formula.

In the above embodiment, the sub arm 4 is supported by the elastic support member 6, but it may be supported by other means such as a knife edge. Further, the auxiliary drive means 7 may be one that applies force to any point on the auxiliary arm 4, and may be one that directly applies force to the second optical system 5.

Furthermore, although the above explanation is for the case where the main arm 2 rotates, the above effect can be similarly obtained even if the main arm 2 does not rotate but moves in parallel on a rail, for example. Can be done.

As explained above, the present invention includes attaching a first optical system including at least a light source to the main arm,
Radial feed is performed by moving this main arm,
A second optical system having at least a focusing lens is attached to a sub-arm supported by a main arm, and focusing and tracking are performed by moving the sub-arm, which reduces the weight of the sub-arm and the second optical system. This makes it possible to achieve faster focusing and tracking. Further, since radial feeding is performed by a drive means different from driving for focusing, etc., stable radial feeding can be performed without interference.

Furthermore, in the present invention, since the allowable movement amount of the second optical system (focusing lens) can be increased, the tracking control range is widened, and the accuracy of radial feeding can be lowered.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of the optical system drive device according to the present invention, which is embodied as an optical pickup, and FIG. 2 is a sectional view showing an example of the first optical system in FIG. , FIG. 3 is a main part configuration diagram showing an example of the sub-driving means in FIG. 1, and FIG. 4 is an explanatory diagram for explaining the configuration of FIG. 1. DESCRIPTION OF SYMBOLS 1...Main driving means, 2...Main arm, 3...First optical system, 4...Sub-arm, 5...Second optical system, 5a...Focusing lens, 6...Support, 7 ……
Sub-driving means, 8...driving arm.

Claims (1)

[Claims] 1. A main drive means, a main arm driven by the main drive means on a plane substantially parallel to the disk surface,
a first optical system attached to the main arm and having at least a light source therein; a sub-arm supported by the main arm; and a first optical system attached to the sub-arm in a positional relationship facing the first optical system. , a second optical system having at least a converging lens that receives the light flux emitted from the first optical system and forms a beam spot on the disk surface; and a sub-drive that directly or indirectly drives the second optical system. and a distance between the center of rotation of the second optical system by the sub-driving means in a plane substantially parallel to the disk surface and the center of the focusing lens of the second optical system.
An optical system driving device characterized in that L ₁ is selected to be approximately ΔL larger than a distance L ₂ between the center of rotation and the center of a light beam emitted from the first optical system. However, ΔL=L ₁ −√ ₁ ² −(2-2) ² D; effective diameter d of the light beam emitted from the first optical system; effective diameter of the focusing lens