JPH0235632A - Actuator - Google Patents

Abstract

PURPOSE:To attain miniaturization and light weight and to obtain a high frequency characteristic by providing a mirror to introduce a beam in the direction of an objective lens at a lens holder. CONSTITUTION:A lens 7 is provided at the lower part of the lens holder 1 that is a movable member, and also, the lens holder 1 is formed in almost a box opened in an incident direction of the beam from a light source 3, and the mirror 6 to introduce the beam in the direction of the objective lens is provided in the inside of the box in such a way that it keeps a non-contact state with the inside of the box. By employing such structure, it follows that the beam from the light source 3 is introduced to the objective lens 7 via the mirror 6 in the lens holder, which can set the lens holder 1 lower than the objective lens 7 in a direction of optical axis. In such a way, the miniaturization can be attained, and also, it is possible to drive the objective lens 7 in a focusing direction and a tracking direction with high accuracy and with a comparatively small current.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a method for driving an objective lens that irradiates a light spot onto a recording medium in a focusing direction parallel to the optical axis and in a tracking direction perpendicular to this. This is related to the actuator that has been developed.

[Conventional technology]

Various actuators have been proposed in the past.

For example, an objective lens is attached to the upper center of a lens holder, and this lens holder is connected to a relay member via a pair of focusing plate springs, and this relay member is connected to a post provided via a pair of tracking plate springs. There is one in which the objective lens is supported so as to be movable in the focusing direction and the tracking direction. Focus coils are provided on both sides of the lens holder facing each other in the tracking direction, and tracking coils are provided on each focus coil, and the base has a permanent magnet that cooperates with these focus coils and tracking coils. A magnetic circuit is provided. There is also one in which the objective lens is driven in the focusing direction and the tracking direction by the electromagnetic interaction between the current flowing through the focusing coil and the tracking coil and the magnetic circuit.

[Problem to be solved by the invention]

However, in the conventional actuator described above, a mirror for guiding the beam emitted from the light source is provided in the objective lens on the opposite side of the objective lens in the optical axis direction of the lens holder, and the inside of the lens holder body is used as an optical path. There is. Therefore, there is a problem in that the dimension of the lens holder in the optical path direction becomes large, and the entire actuator becomes large. In addition, since a space is formed in the lens holder body to provide an optical path, the lens holder cannot have sufficient rigidity, which causes unnecessary high-order resonance and improves the accuracy of focus and tracking control. There is a problem that the amount decreases.

Furthermore, with conventional actuators, the weight of the entire lens holder including the tracking coil and focus coil is large, making it impossible to obtain high frequency characteristics, and requiring a relatively large current for driving. .

The present invention is proposed to solve the above problems,
The object of the present invention is to provide an actuator that can be miniaturized and can drive an objective lens in a focusing direction and a tracking direction with high precision and with a relatively small current.

[Means and effects for solving the problems] In order to achieve the above object, the present invention comprises a movable member having an objective lens which is movably supported by an elastic support and forms a light spot on a recording medium; In an actuator in which an electromagnetic drive section having a focusing coil, a tracking coil, and a magnetic circuit is provided on both sides of a movable member in a direction substantially perpendicular to the optical axis direction, a lens is provided below the lens holder of the movable member, and the lens holder is separated from the light source. It is formed into a substantially box shape with an opening in the direction in which the beam enters, and a mirror that guides the beam toward the objective lens is provided inside the box shape in a non-contact state with the inside of the box shape.

By doing so, the beam from the light source is guided to the objective lens via the mirror in the lens holder, and the lens holder can be lowered in the optical axis direction of the objective lens.

Furthermore, since the lens holder is shaped like a reinforced box, the rigidity of the lens holder can be improved.

〔Example〕

FIG. 1 and subsequent figures show one embodiment of the present invention, and FIG. 1 is a side view showing the relationship between the lens holder l and the optical system. In this embodiment, information is reproduced from the optical card 2. To explain the optical path of the optical system, the beam from the semiconductor laser 3 is collimated by the collimator lens 4, passes through the X-F mirror 5, is reflected downward by the mirror 6, and passes through the objective lens 7 to the optical card. 2 from a direction substantially normal to the optical card 2, and an image is formed on the optical card 2.

The optical path of the reflected light from the optical card 2 is as shown in the bottom view shown in FIG. It has become.

Next, the electromagnetic drive unit will be described. As shown in FIG. 2, magnetic circuits are formed on both sides of the lens holder 1 having the objective lens 7. In other words, one of the outer yokes 9, the permanent magnet 11, and the inner yoke 10
2. Forms a closed loop magnetic circuit that generates a magnetic flux that crosses the tracking coil 13, and generates a magnetic flux that crosses the focus coil 17 and the tracking coil 18 by the other outer yoke 14, permanent magnet 15, and inner yoke I6. A magnetic circuit is formed, and the movable member, and thus the objective lens, is driven in the focusing direction and the tracking direction by the electromagnetic action of these magnetic circuits and the current flowing through the focus coil and the tracking coil. In this case, by forming the focus coil and tracking coil as shown in Fig. 3,
It is possible to reduce the weight of the entire lens holder and improve production efficiency. In other words, the focusing coil (Fig. 3A) is fixed to the left and right sides of the lens holder, and the tracking coil (Fig. 3B) formed of a flexible coil is fixed to the left and right sides of the lens holder.
) to hold the focusing coil. FIG. 4 shows a state in which both coils are fixed.

In this case, by forming the inner surface of the tracking coil 13.18 that holds the focus coil 12.17 to be on the same plane as the fixed surface of the lens holder 1, the trunking coil can be separated from the fixed point of the lens holder. Peeling can be prevented as much as possible. Further, as shown in FIG. 4B, a recess 24 is formed in the lens holder 1 where the focus coil 12.17 is joined, and one side of the focus coil that is not in contact with the tracking coil is fitted into this. This allows the focus coil to be attached stably.

In addition, as shown in FIG. 3A, the focus coils 12, 1
7, by forming both at the same time and connecting them in advance, it is possible to simplify the wiring process when forming the electromagnetic drive section and to maintain a balance between both coils. In addition to forming the tracking coils as shown in FIG. 3B, coils may be formed on the left and right sides so that two pairs of coils are located in the magnetic field section.

Each of these coils has one end fixed to the wire stand 20 and the other end electrically connected to the wire 19 fixed to the lens holder l. That is, two of the wires I9 are connected to the tracking coil 13.18, and the other two are connected to the focus coils 12.17 and 41111, so that current for driving the lens holder can be supplied. The wire 19 is fixed to the lens holder 1 and the wire stand 20 so that the actuator can move in the focusing direction and the tracking direction. As shown in Figure 4, holes are formed in the four corners of the box shape of the lens holder 1, the ends of the wires are passed through these holes, and the ends of the wires are fixed, and the ends of the wires that have passed through the holes are passed through the holes formed in the flexible coil and soldered. The attachment is fixed with etc.

By forming in this manner, wire attachment can be performed efficiently and reliably, and conduction of the wires that also serve as electrical connections can be ensured.

Next, the lens holder 1 will be described. The main body is formed in a box shape with an opening in the direction in which the light beam from the light source enters, and the objective lens 7 is provided at the bottom part 21 of the main body.

The center of this objective lens is located slightly shifted from the line connecting the centers of the focus coils 12 and 17 located on both sides of the lens holder 1 in the direction of the beam. The reason why the lens holder 1 is formed in this way is that since there is a wall on the side opposite to the opening of the lens holder 1, the weight is placed on the wall side, making it impossible to maintain balance. Therefore, balance is achieved by shifting the relatively heavy objective lens 7 as described above and installing it in the lens holder l.

A wide space is formed above the objective lens 7 in the optical axis direction, and a mirror 6 of the optical system supported by the other part of the actuator is used in this space to reflect the beam from the semiconductor laser 3 so that it passes through the objective lens 7. Furthermore, it is provided in the lens holder l in a non-contact manner so that the reflected light reflected from the optical card 2 is reflected in the direction of the photodetector 9. Lens holder 1
To ensure rigidity, ribs and the like are formed within a range that does not contact the mirror even when the mirror is moved during driving. In this embodiment, a diagonal rib 22 is provided to be inclined upward from the mirror 6 arrangement position and is inserted into the lens holder 1 from the upper part of the wall on the side opposite to the opening of the lens holder I so as to substantially follow the inclination angle of the mirror 6. It is located at the front of the top. This makes it possible to prevent unnecessary high-order resonance from occurring. Note that the inspection hole 23 formed in the rib 22 guides and detects the beam so as to ensure an appropriate amount of light from the semiconductor laser 3, and the detection result indicates that the light ff13J! This is for an inspection device that is controlled to make adjustments. Since the specific configuration for this purpose is well known, the explanation will be omitted.

〔Effect of the invention〕

As described above, according to the present invention, since the mirror is provided within the box shape of the lens holder, the actuator can be made smaller.

Furthermore, since the electromagnetic drive sections are provided on both sides of the lens holder, the permanent magnets can be made small, the weight of the actuator can be reduced, high frequency characteristics can be obtained, and current consumption for driving can be reduced. Furthermore, since the lens holder is box-shaped and has reinforcing ribs, the plasticity of the lens holder is improved and unnecessary high-order resonance can be prevented from occurring.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of the vicinity of a lens holder according to an embodiment of the present invention, FIG. 2 is a bottom view thereof, FIG. 3 is a perspective view of a focusing coil and a tracking coil, and FIG. 4 is a perspective view of a focusing coil and a tracking coil. , is a perspective view of the vicinity of the lens holder.

Claims (1)

[Scope of Claims] 1. A movable member that is movably supported by an elastic support and has an objective lens that images a light spot on a recording medium, and both sides of the movable member in a direction substantially perpendicular to the optical axis direction of the objective lens. In an actuator that is equipped with an electromagnetic drive unit having a focusing coil, a tracking coil, and a magnetic circuit, a lens is provided at the bottom of a lens holder of a movable member, and the lens holder is shaped like a box with an opening in the direction in which the beam from the light source enters. What is claimed is: 1. An actuator formed in a box-shaped structure, characterized in that a mirror for guiding a beam toward an objective lens is provided inside the box-shaped interior in a non-contact state with the box-shaped interior.