JPS62262017A - Optical head actuator - Google Patents

Abstract

PURPOSE:To obtain a small-sized optical head actuator without causing any beam shift by using a reflecting mirror supported by a pair of lamination type piezoelectric elements for generating a difference in height by a difference in voltages impressed on the lamination type piezoelectric element. CONSTITUTION:Both end parts of a reflecting mirror 1 are supported by a pair of lamination type piezoelectric elements 11, 12 which have been provided on a fixed base 9, and by an electric conduction to the lamination type piezoelectric elements 11, 12, the reflecting mirror 1 is driven in the directions as indicated with arrows A-A' centering around an aerial revolving shaft 0' and a light beam 7 is brought to an access. The lamination type piezoelectric elements 11, 12 are roughly proportional to magnitude of an impressed voltage, and stature, namely, height h1 and h2 are varied to h1' and h2', respectively. Accordingly, by controlling a value of the voltage applied to the lamination type piezoelectric element 11 and 12, a rotational angle theta of a galvanomirror 10 and a position of O which becomes a turning center can be changed freely.

Description

[Detailed Description of the Invention] [Summary] The optical head actuator of the present invention includes a galvano mirror.
A pair of laminated piezoelectric elements whose length, or height, changes in accordance with the applied voltage are used as driving means for the reflecting mirrors constituting the device.

Then, by applying different voltages to the piezoelectric elements, the reflecting mirror performs an operation as if a rotation axis exists, that is, a rotation movement about an imaginary rotation axis.

This eliminates the need for the support arm and rotation shaft for the reflecting mirror, making it possible to reduce the size and weight of the optical head actuator.

[Industrial application field]

The present invention relates to the improvement of an optical head actuator installed in an optical disc device, and in particular, by devising a driving method for a reflecting mirror that controls scanning of a light beam, the optical head actuator is miniaturized, and at the same time, the disc surface is This invention relates to an optical head actuator with improved utilization.

(Prior Art) Beam access using a conventional galvanometer mirror will be explained with reference to FIGS. 4 and 5.

FIG. 4 is a schematic diagram of beam access using a galvano mirror, and FIG. 5 is a perspective view showing an example of the configuration of a conventional galvano mirror.

In these figures, 2 is the mirror rotation wheel, 3 is the objective lens, 4 is the coil, 5 is the magnetic circuit, F is the image side focal position of the objective lens, r is the image side focal length of the objective lens, and U is the objective lens. The optical axis, l is the distance from the image side focal position to the point where the optical axis intersects the reflecting mirror, 0 is the rotation center of the reflecting mirror, θ
represents the rotation angle of the reflecting mirror, and δ represents the amount of disk eccentricity.

As shown in FIGS. 4 and 5, the galvanometer mirror 10 is
The rotation angle θ of the reflecting mirror 1 is controlled by the amount of current flowing through the coil 4.

However, in the case of a conventional galvanometer mirror, a beam shift E is caused by accessing the light beam 7, as shown in FIG.

For example, if we calculate the beam shift E when accessing the disk eccentricity δ = 0.05 mm, it will be 0.23 mm, and the return light from the optical disk 15 will naturally move on the photodetector (not shown). Light beam 7 is on disk 1
Unless the incident light is perpendicular to the surface of 5, the incident light and the returned light will not be destroyed.) This becomes an offset amount of the track error signal and causes deterioration of track followability.

The height h (see FIG. 5) of the galvano mirror 10 constructed in this way is approximately 15 In111.

FIG. 6 is a schematic diagram showing an example of the configuration of a galvano mirror in which no beam shift occurs. In other words, the figure shows the relative positional conditions between the galvano mirror and the objective lens to prevent the occurrence of beam shift. It is a diagram. Note that the condition is that the relationship a=f"·l is maintained between the two.

FIG. 7 is a perspective view showing an example of the shape of the objective lens.
In this example, the diameter d of the objective lens is approximately 6.5 mm,
The height h' is about 4 arms, and the distance f' from the lens end face K to the focal point F is about 2 mm, so it has already been miniaturized.

[Problem that the invention seeks to solve]

However, as shown in FIG. 8, the objective lens has a coil 4 surrounding it. Magnetic circuit 5. A plate spring 8 and the like for supporting the objective lens are disposed on the base 9, and are arranged on the base 9 as shown in FIG.
(Example diagram of galvanometer mirror configuration that does not cause beam shift)
If you try to use the configuration shown in , the image side focal position F
Distance l from to the point P where the optical axis U and the reflecting mirror 1 intersect
is as long as 12 to 13 mm, so the total height of the optical head becomes extremely high as 34 to 36 mm as shown in FIG. 9 (a diagram showing an example of the configuration of an optical head actuator).

In addition, the dimension l" corresponds to the distance from the objective lens 3 of the optical disk 15 toward the center of the optical disk 15 to the center O of the rotation axis, so if this dimension is large, the light ≠ the inner side of the disk 15. The optical head can no longer fit in.

This is a very disadvantageous condition from the viewpoint of effective utilization of the disk surface.

The present invention has been made in order to effectively solve two problems of galvano mirrors: the large beam shift, and the large size of the galvano mirror if configured to prevent this from occurring.

[Means for solving problems]

The optical head actuator of the present invention changes the driving method of the reflecting mirror from the conventional method in which there is an actual rotational axis to a driving method that uses a pair of laminated piezoelectric elements and does not require a rotational axis.
As a result, the rotating shaft and the arm for supporting the reflecting mirror are eliminated, making the optical head actuator more compact.

[Effect]

As mentioned above, the reflecting mirror supported by a pair of laminated piezoelectric elements whose heights differ due to the difference in the voltage applied to the laminated piezoelectric elements rotates around an imaginary axis of rotation that does not exist. The light beam can be accessed by rotating and interlocking.

〔Example〕

FIG. 1 is a perspective view of the main part showing the structure of the galvanometer mirror of the present invention, and FIG. 2 is a side view of the main part showing the principle of the invention.
The same reference numerals as in each of the figures used in the explanation so far indicate the same parts.

As shown in FIGS. 1 and 2, in the galvanometer mirror of the present invention, both ends of a reflecting mirror 1 are supported by a pair of laminated piezoelectric elements 11 and 12 disposed on a fixed base 9, and By energizing the type piezoelectric elements 11 and 12, the reflecting mirror 1 moves in the direction of arrow A-A around the imaginary rotation axis θ''.
' direction to access the light beam 7.

The stacked piezoelectric elements 11, 12 change in height, ie, height, radius, +, ht changes to h2', etc. approximately in proportion to the magnitude of the applied voltage.

Therefore, by controlling the value of the voltage applied to the laminated piezoelectric elements 11 and 12, the rotation angle θ of the galvanometer mirror 10 and the position of 0, which is the center of rotation, can be freely changed.

Therefore, the conditions shown in FIG. 6 (a side view of the configuration of a galvano mirror in which no beam shift occurs), that is, a=, /T-.
By satisfying l, it is possible to prevent the beam shift E from occurring. However, when the optical head actuator performs focus access, the image-side focal position F (see FIG. 6) moves up and down, so the length of l actually changes.

In this case, the relationship a-F'·l will collapse, but in this case, for example, the amount of movement of the objective lens 3 is determined from the value of the current flowing through the focus coil (not shown), and the amount of movement of the objective lens 3 is calculated from the value of the current flowing through the focus coil (not shown), and the amount of movement of the stacked piezoelectric element 11 after the height change is determined. The length of a can be changed by adjusting the voltage applied to 12, so a = y/
It is possible to maintain the relationship T-i.

Furthermore, unlike the conventional method in which an arm extends from the rotation center 0 to support the reflecting mirror 1, the present invention does not require the arm itself, so there is no interference between the focus actuator and the arm, and the invention is compact. This makes it easier to

Note that the focus actuator and the first
When the galvano mirror 10 shown in the figure is combined to form an optical head actuator as shown in Fig. 3, its height H will be about 20 ma+, and the value of 12, which is related to how far it can penetrate into the inner side of the disk, will be 8 w+.
In the figure, 6 indicates a reflector and 20 indicates a focus actuator.

〔Effect of the invention〕

According to the present invention, an optical head actuator that does not cause beam shift and is miniaturized can be realized.

[Brief explanation of drawings]

Fig. 1 is a perspective view of the main parts showing the structure of the galvano mirror of the present invention, Fig. 2 is a side view of the main parts showing the principle of the invention, and Fig. 3 is the main part showing the structure of the optical seven-door actuator of the invention. A perspective view, FIG. 4 is a schematic diagram of beam access operation by a galvano mirror, FIG. 5 is a perspective view showing an example of a configuration of a conventional galvano mirror, and FIG. 6 is a schematic diagram of an example of a configuration of a galvano mirror in which no beam shift occurs. , FIG. 7 is a perspective view showing an example of the shape of the objective lens, FIG. 8 is a perspective view showing the structure of the optical head actuator, and FIG. 9 is a schematic diagram of an example of the structure of the optical head actuator. In the figure, 1 is a reflection mirror, 1a is a light reflection surface of the reflection mirror, 2 is a mirror rotation wheel, 3 is an objective lens, 4 is a coil, 5 is a magnetic circuit, 6 is a reflection plate, 7 is a light beam, 8 is a temporary Spring, 9 is a fixed base, 10 is a galvano mirror 1, 11 and 12 are laminated piezoelectric elements, 15 is an optical disk, 15a is a disk surface, 20 is a focus actuator, δ is the amount of disk eccentricity, E is the amount of beam shift, 0 is the galvano mirror − rotation center, 0゛ is the imaginary rotation axis, F is the image-side focal position of the objective lens, f is the image-side focal length of the objective lens, P is the point where the optical axis and the reflecting mirror intersect, θ is the point of the reflecting mirror Rotation angle, a is the distance from the center of rotation of the galvanometer mirror to the point where the optical axis and the reflecting mirror intersect, l is the distance from the image side focal position F to the point where the optical axis and the reflecting mirror intersect, l゛ is F The distance between
, hz' is the height of the laminated piezoelectric element 11゜12 after energization, and ■( is the total height of the optical helide actuator, respectively.) Figure 3 + It'sis7 6 et al. 4. Shiba? -n'ij'Ruba°Nomirror Zhe' Completed 75 times f17 P4F Ltt1, Chosumu Gu Power 'Nombaso S Rariii #Q' (PJm Figure 6

Claims (1)

[Claims] An optical disc device that reads and writes information using a minute light spot on a disc is equipped with a galvanometer mirror (10) for accessing a light beam (7) in the radial direction of the optical disc (15). In the configuration of the optical head actuator, the galvano mirror (10) includes a pair of laminated piezoelectric elements (11) whose height changes depending on the applied voltage;
12) An optical head actuator characterized in that a reflecting mirror (1) is supported by a member.