JP2785202B2 - Optical disk drive - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device suitable for detecting the position of an optical pickup or the like.

[Summary of the Invention]

According to the present invention, in an optical disk device, a light quantity control means is interposed in an optical path between a light emitting element and a pair of light detectors, and a pair of light detectors is provided with relative movement of the light path and the light quantity control means. By changing the detected light amount differentially, an accurate position detection signal can be obtained using a small and inexpensive photodetector even for a moving body having a large displacement amount.

[Conventional technology]

2. Description of the Related Art Conventionally, an optical pickup for reproducing an optical disc is generally slid in the radial direction of the disc by a moving coil type linear motor including a moving coil, a permanent magnet, and a yoke, and then moved by a tracking actuator. Is configured to face the track. In the case of sliding, the position of the optical pickup is detected by, for example, a linear encoder. Alternatively, the position of the optical pickup is detected by integrating speed information obtained from a detection coil coupled to a yoke having the same configuration as the linear motor.

[Problems to be solved by the invention]

However, when the detection coil is used, there is a problem that an expensive element having a considerable volume and weight, such as a yoke and a permanent magnet, is required.

Further, in the case of the linear encoder, there is a problem that an expensive high-resolution one having a large number of detection elements must be used in order to increase the detection accuracy.

In order to solve such a problem, the applicant of the present application
No. 86942 has already proposed the following “optical position detecting device”.

The previously proposed optical position detecting device is movably disposed to face an optical recording medium such as an optical disk, and detects a position of a movable optical system that makes a light beam incident on the optical recording medium with respect to the optical recording medium. A light beam generating unit that causes the position detecting light beam to enter the light reflecting unit, and a light receiving surface unit that is configured to receive the position detecting light beam reflected by the light reflecting unit in the movable optical system and form a beam spot. Using a light detection unit having a light detection unit and a signal processing unit for processing an output signal obtained from the light detection unit, a detection output that accurately represents the position of the movable optical system with respect to the optical recording medium can be obtained. Even when the system moves over a relatively wide range in the optical recording medium, the light receiving surface portion in the light detection section can be made relatively small in size,
It is possible to reduce the size and cost of the light detection unit.

First, the proposed device will be described with reference to FIGS.

FIG. 4 shows the overall configuration of the proposed device, and FIGS. 5 and 6 show the configuration of the main parts thereof.

In FIG. 4, an optical disk D is placed on a turntable (1) and rotated at a predetermined speed by a rotation drive unit (2). The movable optical system (10) arranged opposite to the optical disk D includes an objective lens (11) and a prism (12), and guides the light beam emitted from the light beam generation / detection block (13) to the disk D. At the same time, the light beam reflected by the disk D is returned to the generation / detection block (13). The movable optical system (10) is moved in the radial direction of the disk D by a drive unit (not shown).

Reference numeral (20) denotes a fixed optical system, in which a light emitting element (21) such as a light emitting diode is provided on the side opposite to the light beam generation / detection block (13) with respect to the movable optical system (10). Light emitted from the element (21) is guided to the prism (12) through a slit (23) formed in the flat plate (22),
The light reflected from the prism (12) is guided to the light detection unit (24).

As shown in FIG. 5, the photodetector (24) comprises a pair of photodetectors (25) and (26) each having a right-angled triangular shape, and the oblique sides (25b) and (26b) face each other. Along with
The whole is arranged so as to be rectangular in the moving direction of the movable optical system.

With the sliding of the movable optical system (10), the irradiation area P of the reflected light from the prism (12) moves, and one of the light detection units (24) moves.
Light receiving area of the pair of optical detectors (25) and (26) are differentially changed, the detection signals S ₁ and S ₂ of the pair of levels corresponding to the respective light receiving areas are obtained.

The detection signals S ₁ and S ₂ is supplied to the configuration of the signal processing circuit (30) as shown in FIG. 6, the signal processing as shown in the following equation, the level variation of the signals S ₁ and S ₂ The influence is removed, and the position detection signal Sd accurately corresponding to the position of the movable optical system (10) is obtained.

Sd = (S ₁ −S ₂ ) / (S ₁ + S ₂ ) However, in the above-described proposed device, the length of the pair of photodetectors (25) and (26) of the photodetector (24) is Must be at least equal to the entire moving range of the movable optical system (10). For example, in the case of a compact disk having a diameter of 12 cm, the required length is about 55 mm, and there is a problem that the photodetector is expensive.

Also, this photodetector has a problem that its use efficiency is low because only a part thereof is used at all times.

In view of the foregoing, an object of the present invention is to provide an optical disk device that can obtain an accurate position detection signal using a small and inexpensive photodetector even for a moving body having a large displacement. .

[Means for solving the problem]

According to the present invention, a movable part (10) that holds an objective lens (11) between the light emitting element (41) and moves in the radial direction of the disk D, and emits light toward the movable part (10). A light emitting element (41) for emitting light, a pair of photodetectors (42) and (43) for detecting light emitted from the light emitting element, and a light path between the light emitting element and the pair of photodetectors. An optical disc device comprising light quantity control means (45) and (46) for controlling the light quantity detected by a pair of photodetectors, wherein the pair of photodetectors is a light path and a light quantity control means. Are arranged adjacent to each other in the direction perpendicular to the target moving direction, and the light quantity control means includes a pair of edges (45b) and (46b) whose reference lines (45) are parallel to the relative moving direction.
a) and (46b), the distance between one of the pair of edges and the reference line gradually increases in the relative movement direction over the moving range of the movable part (10), and The distance between the other end of the edge and the reference line is
0) is formed so as to gradually decrease over the moving range of (0). With the relative movement of the optical path and the light amount control means due to the movement of the movable portion (10) in the disk radial direction, the detected light amount via the light amount control means is reduced. The optical disk device uses a difference between detection outputs of a pair of photodetectors that change differentially as a position detection signal.

[Action]

According to the present invention, an accurate position detection signal can be obtained using a small and low-cost photodetector even for a moving body having a large displacement.

〔Example〕

Hereinafter, an embodiment of an optical disk device according to the present invention will be described with reference to FIG.

 FIG. 1 shows the configuration of the main part of an embodiment of the present invention.

In FIG. 1, reference numeral (40) denotes a position detecting optical system as a whole, and a pair of photodetectors (42) and (43) oppose an optical element (41). Are arranged perpendicularly to the moving direction of.

Each flat plate (44) interposed between the light emitting element (41) and the photodetectors (42) and (43) has a right-angled triangular shape.
The pair of slits (45) and (46) make the long sides (45a) and (46a) sandwiching the right angle face each other as a reference line parallel to the moving direction of the movable optical system, and the oblique sides (45b) and (46)
b) are drilled so that they are parallel to each other, leaving a boundary (47).

The intermediate portion (47), the inner ends (42a) and (43a) of the pair of photodetectors (42) and (43), and the light emitting element (41) are aligned on substantially the same plane. Be placed.

 The operation of the embodiment shown in FIG. 1 is as follows.

When, for example, the flat plate (44) moves as the movable optical system (not shown) slides, the light detector (41) emits light from the light emitting element (41) and passes through the slits (45) and (46) to generate a light detector ( Irradiated area P ₄₅ formed on 42) and (43) respectively
And the boundary of the P _46, the hypotenuse of the slit (45b) and (46b)
Moves in the direction of alignment of the two photodetectors (42) and (43). In addition, the irradiation area P with respect to the sliding direction of the movable optical system
The spread of ₄₅ and P ₄₆ is due to the photodetectors (42) and (4
3) Limited by its own width.

Thus, also in the present embodiment, similarly to the above-described proposed example, the light receiving areas of the two photodetectors (42) and (43) are changed differentially, and the level of the level corresponding to each light receiving area is changed. 1
Since a pair of detection signals is obtained, an accurate position detection signal can be obtained by processing the detection signals in the same manner as described above.

According to the present embodiment, the photodetectors (42) and (43) can be significantly reduced in size, used efficiently, and the cost can be significantly reduced.

In the embodiment of FIG. 1, since the boundary (47) exists between the slits (45) and (46), the position adjustment of the photodetectors (42) and (43) is relatively easy. However, even when the long sides (45a) and (46a) of both slits are made to coincide with each other and the boundary (47) is removed, the same operation is performed.

Next, another embodiment of the optical position detecting device according to the present invention will be described with reference to FIG.

FIG. 2 shows the configuration of another embodiment of the present invention. In FIG. 2, portions corresponding to FIGS. 4 and 5 are denoted by the same reference numerals, and redundant description will be omitted.

In FIG. 2, reference numeral (50) denotes a fixed optical system, and a light-emitting element (51) and a pair of photodetectors (52) and (53) are provided with respect to a prism (12) of a movable optical system (10). Both are arranged close to the rotation drive unit (2). (55) and (56) are a pair of mirrors, which are disposed on the side opposite to the disk D with respect to the prism (12).

Like the slits (45) and (46) in the embodiment of FIG. 1, the mirrors (55) and (56) are formed in the shape of a right triangle, and the long sides sandwiching the right angle are moved by the movable optical system (10). They are arranged so as to face each other as a reference line parallel to the direction and leave a slight gap so that the oblique sides are parallel to each other.

Further, the photodetectors (52) and (53) are arranged and arranged with a plane including the gap and the light emitting element (41) interposed therebetween.

With the above arrangement, in the embodiment shown in FIG. 2, the light emitted from the light emitting element (51) is reflected by the prism (12) and reaches a pair of mirrors (55) and (56). Five
The reflected lights of 5) and (56) are further reflected by the prism (12) and reach the photodetectors (52) and (53).

Looking at the optical path between the light emitting element (51) and the photodetectors (52) and (53), the reflection by the prism (12) is such that the light emitting element (51) and the photodetector are located symmetrically with respect to the reflecting surface. This is equivalent to the transfer of (52) and (53), and the reflection by the mirror is such that the light-emitting element (51) and the pair of photodetectors (52) and (53) are arranged on both sides of the mirror. It is equivalent to

That is, the light emitting element (51) and the pair of photodetectors (52) and (53) in the embodiment of FIG. 2 are optically similar to the embodiment of FIG. They face each other via (55) and (56), and the light receiving area of each photodetector (55) and (56) changes differentially according to the movement of the movable optical system (10).

Thus, in the embodiment shown in FIG. 2, similarly to the embodiment shown in FIG. 1, a large displacement can be accurately detected by using a small and inexpensive photodetector.

As described above, the present invention has been described with respect to the case where the moving body makes a linear motion. However, in the case of turning, the arc-shaped slits (45C), (46) are formed in a fan-shaped flat plate (44C) as shown in FIG.
Light amount control means in which C) are formed in opposite directions can be used.

In the embodiments of FIGS. 1 and 2, the displacement amount of the moving body and the light reception amount of the photodetector are in a linear relationship. However, for example, by setting the hypotenuse of each slit to an appropriate curve,
Arbitrary position detection characteristics can be realized.

〔The invention's effect〕

As described in detail above, according to the present invention, the light amount control is performed on the optical path between the light emitting element that holds the objective lens and emits light toward the movable portion that moves in the radial direction of the disk and the pair of photodetectors. The light quantity detected by the pair of photodetectors is changed differentially with the interposition of the light path and the light quantity control means relative to the relative movement of the light path and light quantity control means. An optical disk device that generates an accurate position detection signal using a low-cost photodetector can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a configuration of a main part of one embodiment of an optical disk device according to the present invention, FIG. 2 is a sectional view showing a configuration of another embodiment of the present invention, FIG. 3 is a plan view showing a configuration of a main part of still another embodiment of the present invention, FIG. 4 is a cross-sectional view showing a configuration example of an optical disk device according to the proposed method, and FIG. FIG. 6 is a perspective view showing a configuration of a part, and FIG. 6 is a block diagram showing a configuration of another main part of the proposed example. (10) is a movable optical system, (20) and (50) are fixed optical systems,
(21), (41) and (51) are light-emitting elements, (25), (26),
(42), (43), (52), and (53) are photodetectors, (30) is a signal processing circuit, (40) is a position detection optical system, (45), (45)
C), (46) and (46C) are slits, and (55) and (56) are mirrors.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01D 5/34-5/36

Claims (1)

(57) [Claims] 1. A movable portion that holds an objective lens and moves in a radial direction of a disk, a light emitting element that emits light toward the movable portion, and a pair of photodetectors that detect emitted light of the light emitting device. An optical disc device comprising: a light amount control unit that controls the amount of light detected by the pair of photodetectors through an optical path between the light emitting element and the pair of photodetectors. A pair of photodetectors are arranged adjacent to each other in a direction perpendicular to the relative movement direction of the optical path and the light quantity control means, and the light quantity control means has a pair of edges parallel to the relative movement direction. The distance between one of the pair of edges and the reference line gradually increases in the relative movement direction over the range of movement of the movable portion, and the pair of edges The distance between the other of the above and the reference line is The light amount is formed so as to gradually decrease over the moving range of the movable portion, and the amount of light detected via the light amount control device is associated with the relative movement of the optical path and the light amount control device due to the movement of the movable portion in the disk radial direction. An optical disc device, wherein a difference between detection outputs of the pair of photodetectors that changes differentially is used as a position detection signal of the movable portion.