JP3006987B2 - Optical pickup - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup of a separation optical system used in an optical disk apparatus, and more particularly to an optical pickup provided with position detecting means for detecting a moving position of a movable optical section.

[0002]

2. Description of the Related Art Recently, optical discs capable of recording a large amount of information at a high density have been used in many fields. Such an optical disk is an optical information recording medium having excellent features that information can be recorded and reproduced in a non-contact manner and that the medium can be exchanged, and thus is attracting attention particularly as an optical file and an external storage medium of a computer. ing.

In an optical disk, information is recorded or reproduced by an optical pickup using a semiconductor laser as a light source, for example, and the information once recorded is erased or rewritten depending on the medium. In this type of pickup, high-speed access is an extremely important factor. However, it has been said that the optical pickup is not suitable for high-speed access because the optical pickup is larger and heavier than a magnetic head used for a hard disk or the like.

In order to solve this problem, an optical system includes a fixed optical section having a light source and a light detecting section for detecting light reflected from an optical disk, and a movable optical section having a light deflecting means and an objective lens. There has been proposed an optical pickup of a separation optical system which is separated into the following.

Further, when the movable optical section is accessed in the radial direction of the optical disk, the moving position of the movable optical section, that is, the position of the condensed beam on the optical disk, is required to position the movable optical section accurately at high speed. Therefore, various moving position detecting means of the movable optical unit have been proposed. For example, as a simplified configuration, there is a position detecting unit (moving position detecting unit) in which a beam splitter and a semiconductor position sensor are mounted on a fixed optical unit and a reflecting prism is mounted on a movable optical unit.

FIG. 13 shows a separation optical type optical pickup on which this simplified type position detecting means is mounted. In the figure, a semiconductor laser 1 and the like are mounted on a fixed optical unit 20. The movable optical section 21 is driven by a linear motor (not shown) by a disk (optical disk) 14 indicated by z in the figure.
Can be moved in the radial direction. In addition, disk 1
The direction perpendicular to the surface of No. 4 is denoted by y, and the direction perpendicular to any of the y and z directions is denoted by x. Hereinafter, a schematic operation of the optical pickup will be described.

The light beam emitted from the semiconductor laser 1 in the fixed optical section 20 is converted into a parallel light by a collimating lens 2, then into a circular beam by a shaping prism 3, and then reflected by a polarizing beam splitter 4.
It is separated into ₁ and the transmitted light L _2. The transmitted light L ₂ travels from the fixed optical unit 20 to the movable optical unit 21 in the direction of the moving axis of the movable optical unit 21, that is, in the z direction.

The transmitted light L ₂ guided to the movable optical section 21 is
The light path is changed in the y-direction by the rising 45 ° mirror 11, and subsequently focused by the objective lens 12 on the information recording surface of the disk 14 above, and then reflected by the information recording surface. This reflected light passes through the objective lens 12 again and rises the optical path by 90 ° by the 45 ° mirror 11.
After being modified, again incident on the polarization beam splitter 4 in the fixed optical unit 20, a portion is reflected, Wollaston prism 5, the upper Di Te click <br/> coater 7 passes through the spot lens 6 like Is collected.

On the other hand, a part of the reflected light L ₁ is incident on a photodetector 9 for an automatic output control device (APC) for controlling the optical output of the semiconductor laser 1, and the rest is moved by a reflecting mirror 8 into a movable optical part 21. Is reflected as a light beam L ₁ 'for detecting the moving position in the direction of. The reflected light L ₁ ′ is
The light beam is in the z-direction parallel to the moving axis of the movable optical unit 21, is reflected by the reflecting prism 13 mounted on the movable optical unit 21, and returns to the fixed optical unit 20 again.

Here, the reflecting prism 13 is a wedge prism whose reflecting surface is inclined in a plane parallel to the surface of the disk 14 so that the reflected light is inclined in the x direction with respect to the moving axis of the movable optical section 21. Has become. Therefore, the light reflected by the reflecting prism 13 is incident on the semiconductor position sensor 10 in the fixed optical unit 20 at an angle.

FIG. 14 shows the principle of detection by the position detecting means. The semiconductor position sensor 10 is a one-dimensional sensor that detects a position in the x direction. The light reflected by the reflecting prism 13 is incident on the semiconductor position sensor 10 while being inclined in the x direction with respect to the movement axis of the movable optical unit 21. Therefore, assuming that the inclination angle of the light incident on the semiconductor position sensor 10 is θ, when the movable optical unit 21 moves by the distance 1 in the z direction, the light beam moves by l × tan θ in the semiconductor position sensor 10 in the x direction. I do. Therefore, the semiconductor position sensor 10
, The position of the movable optical unit 21 in the z direction is detected.

[0012]

However, in such a position detecting means of the movable optical unit, as shown in FIG. 15, when the movable optical unit 21 is rotationally displaced around the y-axis,
The inclination angle θ of the light reflected by the reflecting prism 13 changes. Therefore, the light receiving position of the semiconductor position sensor 10 is x
, And an error occurs in the detection position of the movable optical unit 21. Generally, the semiconductor position sensors 10 in the movable optical unit 21 and the fixed optical unit 20 are separated to some extent even when they are closest to each other due to the arrangement of components. Therefore, as the separation distance increases, the shift amount of the light beam increases. As a result, the error of the position signal also increases.

An object of the present invention is to solve the above-mentioned problems of the prior art, and an object of the present invention is to eliminate the influence of rotational displacement of a movable optical unit in an optical pickup of a separation optical system, and to increase the position of the movable optical unit. An object of the present invention is to provide an optical pickup capable of detecting with high accuracy.

[0014]

An optical pickup according to the present invention comprises a fixed optical section having a light source and a light detecting section for detecting reflected light from a disk, a light beam deflecting section and an objective lens. is separated into a movable optical part to be movable in a radial direction, an optical pickup having a position detecting means of the movable optical unit, the said position detection means, the solid
Provided constant light faculties, and means <br/> for separating in a direction different from the light beam entering the light beam from the light source to the objective lens, provided in said solid constant light faculty is separated into said different direction
Light that travels in different directions
Separating the beam, a diffraction grating leads to movable optical part, movable
The two optical beams for position detection are provided in
A plane mirror for projecting light to the fixed optical unit , and the fixed optical unit
And the position detection reflected by the plane mirror
A sensor for receiving each of the light beams for use and detecting the position thereof, thereby achieving the above object.

Further , the optical pickup of the present invention comprises a light source and
And a light detector that detects light reflected from the disc.
Comprising a constant optical unit, a light beam deflecting unit and an objective lens,
To the movable optical section that can move in the radial direction of the disc
An optical pick-up which is separated and provided with a position detecting means for the movable optical unit.
The position detecting means is attached to the fixed optical unit.
Light beam from the light source is incident on the objective lens
Means for separating in a direction different from the light beam, the fixed
The light provided in the optical unit and separated in the different directions
Into two position detection light beams traveling in different directions.
Te, and the wedge prism leading to movable optical unit, the movable
Provided in the optical section and reflects the two position detection light beams
And a flat mirror for guiding to the fixed optical section,
Provided for detecting the position reflected by the plane mirror
A sensor that receives each light beam and detects its position
To achieve the above objectives
Is done.

[0016]

[0017]

[0018]

[0019]

Further, the optical pickup of the present invention comprises: a fixed optical section having a light source and a light detecting section for detecting light reflected from the disk; a light beam deflecting means and an objective lens;
An optical pickup which is separated into a movable optical unit which is movable in a radial direction of the disk and includes a position detecting unit of the movable optical unit, wherein the position detecting unit is provided in the fixed optical unit, The light beam from the light source is separated in a direction different from that of the light beam incident on the objective lens, and guided as a position detection light beam to the movable optical unit side at an angle parallel to the moving axis of the movable optical unit. Means, provided on the movable optical section, for reflecting the position detecting light beam twice ,
To the fixed optical section as reflected light inclined with respect to
Means having two reflecting surfaces, provided on the fixed optical part,
A sensor for receiving the position detecting light beams reflected by the two reflecting surfaces and detecting the position thereof, thereby achieving the above object.

[0021]

[0022]

According to the above arrangement, two light beams inclined in different directions with respect to the moving axis of the movable optical unit enter the fixed optical unit. Therefore, when the moving position of the movable optical unit changes,
The light receiving positions of the two semiconductor position sensors move in different directions. On the other hand, when the movable optical unit is rotationally displaced within the plane including the two separated light beams, the light receiving positions of the two semiconductor position sensors move in the same direction. Therefore, if the moving position of the movable optical unit is detected from the change in the light receiving positions of the two semiconductor position sensors, the change in the light receiving position due to the rotational displacement of the movable optical unit cancels out each other. Therefore, the detected moving position is not affected by the rotational displacement of the movable optical unit.

[0023]

Embodiments of the present invention will be described below.

Reference Example 1 FIG. 1 shows an optical pickup of Reference Example 1 . The configuration other than the position detecting means of this optical pickup is the same as the configuration of the conventional optical pickup of FIG. 13 described above, and the corresponding parts are denoted by the same reference numerals and detailed description thereof will be omitted.

The light emitted from the semiconductor laser 1 in the fixed optical unit 20 is collimated by the collimator lens 2, is shaped into a circular beam by a shaping prism 3, the polarized beam splitter 4 and the reflected light L ₁ transmission It is separated into light L _2. The transmitted light L ₂ is guided from the fixed optical unit 20 to the movable optical unit 21 and is focused on the information recording surface on the disk 14. On the other hand, a part of the reflected light L ₁ is made incident on the APC photodetector 9, and the rest is reflected by the reflection mirror 8 in the direction of the movable optical unit 21 as a light beam for detecting the movement position.

The movable optical section 21 moves in the radial direction of the disk 14, that is, in the z direction. This movement is performed by a linear motor (not shown). The light reflected by the reflection mirror 8 is a light beam in the z direction parallel to the movement axis of the movable optical unit 21. This light beam incident on the movable optical unit 21 is reflected in the direction of the fixed optical unit 20 by the wedge prism 15 mounted on the movable optical unit 21. The wedge prism 15 converts the incident light into two different directions (+ x direction, -x direction) inclined at the same angle θ with respect to the direction of the movement axis of the movable optical unit 21 in a plane parallel to the surface of the disk 14. The light is separated into reflected lights L ₃ and L ₄ and reflected. Then, the two reflected lights L ₃ and L ₄ enter the two semiconductor position sensors 10a and 10b mounted on the fixed optical unit 20, respectively.

FIG. 2 shows the principle of detecting the moving position of the movable optical section 21. FIG. 3 shows the principle on which the influence of the rotational displacement of the movable optical section 21 is eliminated. Two semiconductor position sensors 1
Reference numerals 0a and 10b denote one-dimensional sensors for detecting the position in the x direction, and when the light receiving position moves in the positive x direction, both outputs increase.

Now, assuming that the movable optical section 21 moves from the inner circumference to the outer circumference of the disk 14 by a distance 1 as shown in FIG. 2, the reflected light L ₃ is reflected by the semiconductor position sensor 10a.
Move in the positive direction by l × tan θ. On the other hand, the reflected light L ₄ are moved only in the negative direction the same amount on the semiconductor position sensor 10b. For this reason, the semiconductor position sensors 10a, 1
0b is processed by the differential amplifier 30 to obtain 2
An output corresponding to 1 × tan θ is obtained, and the movement position of the movable optical unit 21 is detected from this output.

Further, as shown in FIG.
Causes a rotational shift about the y-axis, the reflected light L ₃ ,
Any of L ₄ moves by approximately the same amount the semiconductor position sensor 10a, on the 10b in the same direction. Therefore, the output from the differential amplifier 30 hardly changes. Therefore, the detection position of the movable optical unit 21 is hardly affected by the rotational deviation of the movable optical unit 21. Therefore, the movement position can be detected with high accuracy.

Embodiment 1 FIG. 4 shows Embodiment 1 of the optical pickup of the present invention. In Example 1, as a light beam separation means, in place of the wedge prism 15, arranged substantially parallel to the optical path of the light beam L ₁ emitted for the movement axis of the movable optical unit 21 from the fixed optical unit 20 The transmission type diffraction grating 16 is used.

The transmission type diffraction grating 16 converts incident light into an angle θ different in directions (+ x direction, −x direction) different from the direction of the moving axis of the movable optical section 21 in a plane parallel to the surface of the disk 14. The light is separated into + 1st-order light L ₃ ′ and −1st-order light L ₄ ′ inclined by The +1 order light L ₃ ′ and the −1 order light L ₄ ′ are
The light is reflected by the plane mirror 17 mounted on the optical system 1 and enters the semiconductor position sensors 10a and 10b in the fixed optical unit 20, respectively. The plane mirror 17 is arranged at right angles to the movement axis of the movable optical unit 21. Each of the semiconductor position sensors 10a and 10b is a one-dimensional sensor for detecting a position in the x direction, and outputs of the sensors are processed by a differential amplifier (not shown).

[0032] Also in this embodiment 1, in the same manner as in Reference Example 1, the movement position of the movable optical unit 21 is detected from the output of the differential amplifier, moreover, the detection position, the movable optical unit 21
Hardly affected by the rotational deviation of

The same effect can be obtained by changing the transmission type diffraction grating 16 to transmission type wedge prisms 18a and 18b as shown in FIGS.

Reference Example 2 FIG. 7 shows an optical pickup of Reference Example 2. Also, movable light
FIG. 8 shows an optical path when the department 21 is shifted in the rotation direction.
In the second embodiment, the light beam for detecting the moving position, which is incident on the movable optical unit 21, is reflected by the reflecting prism 19 and returned to the fixed optical unit 20.

The reflecting prism 19 has two reflecting surfaces 19a and 19b facing each other at a predetermined angle, and reflects incident light parallel to the moving axis of the movable optical section 21 on the reflecting surfaces 19a and 19b.
Is reflected twice to obtain reflected light inclined with respect to the movement axis. The reflected light is incident on the semiconductor position sensor 10 in the fixed optical unit 20, and the movement position of the movable optical unit 21 is detected from the output.

If the movable optical section 21 is deviated in rotation, the reflecting surfaces 19a and 19b of the reflecting prism 19 are inclined by the same amount in the same direction, so that the movement of the optical axis of one reflecting surface 19a causes the other reflecting surface to move. Absorbed on the slope of 19b. Therefore, the angle of the reflected light from the reflecting prism 19 does not change.
No.

(Embodiment 3 ) FIG. 9 shows an optical pickup of Embodiment 3 . FIG.
Indicates the principle by which the influence of the rotational displacement of the movable optical unit is eliminated. In the third embodiment, the light beam for detecting the moving position is emitted from the fixed optical unit 20 while being inclined in the x direction with respect to the moving axis of the movable optical unit 21. The light beam is received by the semiconductor position sensor 10 mounted on the movable optical unit 21.

According to such a configuration, the moving position of the movable optical section 21 is detected from the output of the semiconductor position sensor 10 and the light receiving position of the semiconductor position sensor 10 is obtained even if the movable optical section 21 is rotated. Does not change. Therefore,
The detection position of the movable optical unit 21 is not affected by the rotational displacement.

However, in the third embodiment , the displacement of the movable optical section 21 in the x direction affects the detection position of the movable optical section 21. To remove this, as shown in FIG.
The light beam incident on the movable optical unit 21 is separated into two beams inclined at the same angle in different directions, each of which is incident on the semiconductor position sensors 10a and 10b, and each output is calculated by a differential amplifier (not shown). To process.

Then, as shown in FIG. 12, even if the movable optical section 21 is displaced in the x direction, the movable optical section 21 moves by the same amount in the same direction at the light receiving position of the semiconductor position sensors 10a and 10b. The output from the dynamic amplifier hardly changes. That is, in the above-described Reference Example 1 and Example 1, the effect of the displacement of the movable optical unit 21 in the x direction is eliminated according to the same principle that the influence of the rotational displacement of the movable optical unit 21 is eliminated. Can be detected.

[0041]

As described above, the optical pickup of the present invention cancels out the influence of the rotational displacement of the movable optical part in the optical pickup of the separation optical system, so that the influence reaches the detection position of the movable optical part. Can be prevented. Thereby, the moving position of the movable optical unit can be detected with high accuracy in a constantly stable state. Therefore, a high-speed and accurate access operation can be performed, so that the reliability of the optical pickup can be remarkably improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an optical pickup of Reference Example 1.

FIG. 2 is a schematic diagram illustrating a principle of detecting a moving position of a movable optical unit in the optical pickup of Reference Example 1.

FIG. 3 is a schematic diagram illustrating a principle of eliminating the influence of rotational displacement of a movable optical unit in the optical pickup according to Reference Example 1.

FIG. 4 is a schematic view showing Embodiment 1 of the optical pickup of the present invention.

FIG. 5 is a schematic view showing another example of the beam separating means in the optical pickup according to the first embodiment.

FIG. 6 is a schematic diagram showing still another example of the beam separating means in the optical pickup according to the first embodiment.

FIG. 7 is a schematic diagram showing Reference Example 2 of the optical pickup of the present invention.

FIG. 8 shows a movable optical unit in the optical pickup of Reference Example 2 .
FIG. 4 is a schematic diagram showing an optical path when the light is shifted in the rotation direction .

FIG. 9 is a schematic view showing an optical pickup of Reference Example 3 .

FIG. 10 is a schematic diagram illustrating a principle of eliminating the influence of rotational displacement of a movable optical unit in the optical pickup of Reference Example 3 .

FIG. 11 is a schematic diagram showing a modification of the optical pickup of Reference Example 3 .

FIG. 12 is a schematic diagram showing a principle of eliminating the influence of rotational displacement of the movable optical unit in the optical pickup shown in FIG.

FIG. 13 is a schematic configuration diagram showing a conventional example of a separation optical type optical pickup provided with a position detecting means for detecting a moving position of a movable optical unit.

FIG. 14 is a schematic diagram showing a principle of detecting a moving position of a movable optical unit in a conventional example.

FIG. 15 is a schematic diagram showing the influence of rotational displacement of a movable optical unit in a conventional example.

[Explanation of symbols]

Reference Signs List 1 semiconductor laser 4 polarization beam splitter 8 reflection mirror 10, 10a, 10b semiconductor position sensor 15 wedge prism (beam separation means) 16 transmission diffraction grating (beam separation means) 18a, 18b transmission wedge prism (beam separation means) 19 reflection Prism (beam reflecting means) 19a, 19b Reflecting surface 20 Fixed optical unit 21 Movable optical unit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-178101 (JP, A) JP-A-63-200327 (JP, A) JP-A-63-211125 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G11B 7/085 G11B 7/09 G11B 7/095 G11B 7/135

Claims (2)

(57) [Claims] 1. A fixed optical section having a light source and a light detecting section for detecting light reflected from a disk, and a movable optical section having a light beam deflecting means and an objective lens and being movable in a radial direction of the disk. An optical pickup provided with position detecting means for the movable optical section, wherein the position detecting means is provided on the fixed optical section, and a light beam from the light source is incident on the objective lens. Means for separating light in a direction different from the direction, and the light separated in the different direction is separated into two position detecting light beams traveling in different directions, and the light is separated to the movable optical unit. A planar grating provided in the movable optical section, for reflecting the two position detection light beams and guiding the same to the fixed optical section; and a planar mirror provided in the fixed optical section and reflected by the planar mirror. The position detection light By receiving each over beam, an optical pickup comprising a sensor for detecting the position. 2. A fixed optical section having a light source and a light detecting section for detecting reflected light from a disk, and a movable optical section having a light beam deflecting means and an objective lens and being movable in a radial direction of the disk. An optical pickup provided with position detecting means for the movable optical section, wherein the position detecting means is provided on the fixed optical section, and a light beam from the light source is incident on the objective lens. Means for separating light in a direction different from the direction, and the light separated in the different direction is separated into two position detecting light beams traveling in different directions, and the light is separated to the movable optical unit. A wedge prism provided on the movable optical section, a plane mirror for reflecting the two position detection light beams to guide the fixed optical section to the fixed optical section, and a wedge prism provided on the fixed optical section and reflected by the plane mirror. The position By receiving the respective output light beam, the optical pickup comprising a sensor for detecting the position.