JPH061555B2 - Optical pickup device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup device used in an optical disc device having a high speed access function.

Configuration of Conventional Example and Problems Thereof In recent years, improvements have been made to shorten the access time of an optical disc. As one of the improvements, among the optical members constituting the optical pickup, the objective lens (convex lens for converging light on the optical disk) and a few optical members required for light transmission are sent by the motor, and other optical members are used. A method has already been proposed in which the movable mass is reduced in weight by fixing the objective lens in a state where the light rays can be reliably exchanged with the objective lens, and as a result, the optical pickup can be moved at high speed. The method of forming such an optical member will be referred to as a separation optical system. Among them, the optical pickup device (rotary optical pickup device) that rotates the objective lens around a certain axis to access the track on the disc is mechanically simple and has little rattling. It can be said that this is the most suitable pickup device to use.

An example is shown in FIG. 1A and 1B are a partially cutaway top view and a side sectional view of a rotary optical pickup device (hereinafter referred to as a separate rotary optical pickup device) which is an improvement of a conventional optical pickup device using a split optical system. The figure is shown. In FIG. 1, 1 is an objective lens, 4 is a fixed optical system composed of a laser emission source 4a, a collimator lens 4b, a spectral member 4c, a condenser lens 4d, and a light receiving element 5. Reference numeral 2 is a photoconductive member provided for the purpose of coupling the optical axes of the objective lens 1 and the fixed optical system 4, and has two reflecting means (reflection surfaces) 2a and 2b set in parallel,
Moreover, it is characterized by being formed of a transparent member such as glass. Reference numeral 3 is a rotating member for setting the photoconductive member 2 to be rotatable.

The operation of the separate rotation type optical pickup device which is an improvement of the conventional optical pickup device configured as described above will be described below.

The light emitted from the laser emission source 4a is collimated by the collimator lens 4b and then passes through the spectroscopic member 4c to reach the photoconductive member 2. The light incident on the photoconductive member 2 is reflected by the two reflecting surfaces 2b and 2a provided in parallel with each other, enters the objective lens 1, and is condensed on the optical disc 10. The light reflected after reading the information written on the optical disk 10 (unevenness on the disk surface, difference in reflectance, etc.) travels in the direction opposite to that at the time of incidence, and is directed toward the condenser lens 4d by the spectral member 4c. Is changed, and finally the light receiving element 5 converts the signal into an electronic signal.

Objective lens 1 for checking the information on the optical disk 10
Is moved over all tracks, the photoconductive member 2 and the objective lens 1 are rotated about the rotation axis P of the rotation member 3. The parallelism of the reflecting surfaces 2a, 2b is sufficient,
Moreover, if the optical axis Q passing through the center of the objective lens 1 and the rotational axis P coincide with each other, the fixed optical system 4, the photoconductive member 2, and the optical axis of the objective lens 1 are irrespective of the rotation of the photoconductive member 2. The mutual relationship is kept unchanged (having a rotation-invariant optical axis). That is,
Looking through the reflecting surface 2b from the fixed optical system 4, the center of the objective lens 1 looks as if it is on the rotation axis P, and even if the objective lens 1 and the photoconductive member 2 rotate. That is, the objective lens 1 just appears to rotate about its optical axis. Therefore, even if the objective lens 1 and the photoconductive member 2 are rotated, the light reflected by the optical disk 10 always returns to the same point on the light receiving element 5, so that reading / writing of information is always performed in the same state with respect to any track. it can.

However, in order to keep the mutual relationship of the optical axes of the respective optical systems unchanged, the two reflecting surfaces 2a and 2b must be parallel to each other with considerable accuracy. Therefore, if the photoconductive member 2 is constructed by mounting the reflecting surfaces 2a and 2b on the rigid body as reflecting plates, sufficient accuracy cannot be obtained, and when the track is accessed, a strong acceleration is applied to the photoconductive member 2. Therefore, the strength is insufficient.

Therefore, in the separation rotary type pickup device which is an improvement of the conventional optical pickup device, the light conducting member 2 is used as the light conducting member 2 in FIG.
We decided to use a glass rod (parallelogram prism) with a parallelogram cross-sectional shape as shown in. By introducing this parallelogram prism, a great effect can be obtained in terms of optical axis alignment and strength.

However, in the conventional improved example, reflection on the incident surfaces 2u and 2v (upper bottom surface and lower bottom surface) of the parallelogram prism that constitutes the photoconductive member 2 may adversely affect the normal operation of the optical pickup device. It was This is shown in FIG. 3a. The photoconductive member 2 formed of a parallelogram prism was installed perpendicular to the incident optical axis in the conventional improved example.
This is because the upper end surface of the rotating member 3, which is generally composed of a bearing or the like, is formed so as to be perpendicular to the rotating shaft center P, so that the parallelogram prism is designed to be parallel to the upper end surface ( Therefore, it was very natural to install it (perpendicular to the axis of rotation).

However, as a result, the light returning from the objective lens 1 (signal light) and the light reflected by the incident surfaces 2u and 2v of the photoconductive member 2 (unnecessary reflected light) are incident on the light receiving element 5 together. Moreover, due to a slight deviation of the optical axes of the signal light and the unnecessary reflected light, an image T of the unnecessary reflected light can be formed at a position apart from the image formation S of the signal light.

Now, consider the case where the photoconductive member 2 is rotated for track access. Since the optical axis of the signal light is invariable with respect to the rotation as described above, the image formation S does not move. However, since the optical axis of the unnecessary reflected light is deviated from the rotation-invariant optical axis, the position of the image formation T differs depending on the rotation angle.

When the unnecessary reflected light is incident on the light receiving element 5 in this manner, an electrical offset is added to the output as a result. Further, the offset amount varies depending on the rotation angle of the photoconductive member 2.

The light receiving element 5 is used for signal detection and at the same time the optical disc 1 is used.
It is also used as a position detecting means in the objective lens control for correctly focusing on the 0 track. Although details are not described here, the light receiving element 5 is generally composed of a plurality of photoelectric conversion elements, and a focus error and a tracking error can be detected by taking an appropriate difference between the elements. Here, when the image formation T of the unnecessary reflected light is moved by the rotation of the photoconductive member 2, especially when it is moved between the elements which have mutually different outputs, the offset amount of the position detection output greatly changes, As a result, an error will occur in focus control and tracking control.

If the optical axis of the unnecessary reflected light does not change and the image can be formed at the same position as the signal light, the offset does not change due to the rotation. However, in order to make the optical axes of the unnecessary reflected light and the signal light coincident with each other and to make them invariable in rotation, it is not a very feasible method because processing accuracy and mounting accuracy of the photoconductive member 2 are required to be strict.

An object of the present invention is to improve the conventional optical pickup device by eliminating the influence of unnecessary reflected light in the separate rotary optical pickup device, and always operate in a stable state regardless of the rotation of the photoconductive member due to track access. The present invention is to provide an optical pickup device.

According to the present invention, there is provided a photoconductive member comprising a rotating member having a rotational degree of freedom for moving an objective lens in an arc shape, and having a first reflecting surface and a second reflecting surface set in parallel therewith. A member is provided, and the objective lens and the first and second reflecting surfaces are sequentially arranged in a line along the optical axis, and the second reflecting surface is arranged on the turning axis of the turning member. Further, a fixed optical system having a light emitting means and a light receiving means provided outside the rotating member and the second reflecting surface are optically coupled to each other, and the photoconductive member includes the first and the first light transmitting members. 2 is formed of a rod-shaped transparent material having a reflecting surface, and the photoconductive member is provided so that its bottom surface is inclined with respect to a plane perpendicular to the rotation axis of the rotation member. An optical pickup device characterized in that it reflects on the surface of the photoconductive member. By largely separating the optical axis of the unnecessary reflected light from the optical axis of the signal light returning from the optical disc, it is possible to prevent the unnecessary reflected light from entering the light receiving element and causing an offset in the output signal, and to prevent the rotation of the photoconductive member. The present invention realizes an optical pickup device in which an offset variation due to a dynamic angle does not occur.

Description of Embodiments FIG. 2 is a side sectional view of an embodiment of an optical pickup device according to the present invention.

The components are similar to the conventional improvements. A feature of the present invention is that the optical axis of the light emitted from the fixed optical system 4 toward the photoconductive member 2 is not perpendicular to the incident surfaces 2u and 2v of the photoconductive member 2, and This is because the lower bottom surface is provided so as to be appropriately inclined with respect to the rotation plane of the rotation member 3.

The effect of this is shown in FIG. 3b. Even if the photoconductive member 2 is installed so as to be inclined, the reflecting surfaces 2a and 2b are parallel to each other, and the optical axis of the light emitted from the fixed optical system 4 and the rotation axis P of the photoconductive means 2 coincide with each other. If so, the optical axes of all these optical systems are rotationally invariant, so that the image S of the signal light is kept in a fixed position on the light receiving element 5. In the conventional improvement example, the problem T occurs because the image T of the unnecessary reflected light is mixed in the light receiving element 5, but in the present embodiment, the photoconductive member 2 is designed so that the incident surfaces 2u and 2v and the optical axis are not perpendicular to each other. Since the optical axis of the unnecessary reflected light is largely deviated from the optical axis of the signal light because the optical axis of the unnecessary reflected light is inclined with respect to the rotation plane, the image T of the unnecessary reflected light is not formed in the light receiving element 5. Does not happen. Therefore, the offset due to the unnecessary reflected light as described in the conventional improvement example does not occur.

As described above, according to this embodiment, the incident surfaces 2u and 2v are appropriately inclined with respect to the rotating plane so that the incident surfaces 2u and 2v do not intersect perpendicularly with the incident optical axis.
It is possible to prevent unnecessary reflected light from entering the light receiving element 5.

In the present embodiment, the means for inclining the photoconductive member with respect to the rotating plane of the rotating member 3 was not specified, but the second means was used.
In the figure, the photoconductive member 2 is provided between the photoconductive member 2 and the rotating member 3.
A member (not particularly numbered) for inclining and fixing is provided. However, the method described in the figure is the photoconductive member 2
The attachment method of is not limited.

Further, the configuration of the optical element in the fixed optical system 4 in FIG. 2 is not limited, as long as it has at least a light emitting source (not limited to a semiconductor laser) and a light receiving source.
The fixing method of the objective lens 1 was also not mentioned,
This may also be positioned in some way with respect to the photoconductive member 2 so as to interlock with the photoconductive member 2 during track access.

EFFECTS OF THE INVENTION As described above, according to the present invention, a transparent member having a parallelogram cross-sectional shape having two reflecting surfaces facing each other in parallel is used as the photoconductive member of the split rotation type optical pickup device. Moreover, since the photoconductive member is installed so as to be inclined with respect to the plane perpendicular to the rotation axis, it is not only structurally simple and strong, but also unnecessary reflection reflected by the incident surface of the photoconductive member. It is possible to realize an optical pickup device in which light does not enter the light receiving element, and therefore, the offset fluctuation of the output signal does not occur due to the rotation of the photoconductive member.

[Brief description of drawings]

1A and 1B are a partially cutaway top view and a side sectional view, respectively, of a separation-rotation type optical pickup device which is an improvement of the conventional optical pickup device, and FIG. 2 is a side view of the optical pickup device in one embodiment of the present invention. FIG. 3 is a sectional view showing the principle of operation. 1 ... Objective lens, 2 ... Photoconductive member, 2u, 2v ...
Incident surface, 3 ... Rotating member, 4 ... Fixed optical system, 5 ... Light receiving element.

Claims (1)

[Claims] 1. A photoconductive member comprising a rotary member having a rotary degree of freedom for moving an objective lens in an arc shape and having a first reflective surface and a second reflective surface set in parallel therewith. The objective lens and the first and second reflecting surfaces are sequentially arranged in a line along the optical axis, and the second reflecting surface is arranged on the turning axis of the turning member. Further, a fixed optical system having a light emitting means and a light receiving means provided outside the rotating member is optically coupled to the second reflecting surface, and the photoconductive member is formed by the first and second reflecting members. The surface is formed of a rod-shaped transparent material, and the photoconductive member is provided so that its bottom surface is inclined with respect to a plane perpendicular to the rotation axis of the rotation member. Optical pickup device.