JP2578238Y2 - Signal detection system of optical disk device - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal detection system of an optical disk apparatus for separating a signal related to servo error detection from a reflected light beam of an optical disk.

[0002]

2. Description of the Related Art A signal detection system of an optical disk device generates a focus error signal and a track error signal as signals related to servo error detection. The focus error signal is generated by condensing a light beam reflected by the optical disk, guiding the light beam to a light receiving element for error detection, and calculating a signal from each divided region of the light receiving element.

There are several methods for detecting a focus error. For example, there is a method for detecting a focused state of an objective lens by converging a light beam reflected from an optical disk and detecting the size of the spot. This focus error detection method is called a spot size method.

FIG. 7 shows an example of a signal detection section used in a signal detection system of an optical disk device using the spot size method. A reflected light beam from the optical disk is transmitted through a prism block (not shown) and enters the signal detection unit. The incident light flux passes through a half-wave plate 81, is condensed by a condenser lens 82, and is incident on a polarizing beam splitter prism (PBS prism) 83.

[0005] A PBS prism 83 separates the incident light beam into P and S polarized components orthogonal to each other, a light receiving element 84A of the composite sensor 84 receives the P polarized component from the PBS prism 83, and a light receiving element 84B converts the S polarized component. Receive light. The light receiving elements 84A and 84B convert the received polarization components into electric signals and send the electric signals to the processing unit 90.

The processing section 90 generates a focus error signal FE based on the output from the composite sensor 84 and outputs the focus error signal FE to a reproducing circuit and a servo circuit (not shown).

[0007]

By the way, in the signal detection system of the optical disk device shown in FIG. 7, two light receiving elements 84A and 84B are connected to one to reduce the number of elements used in the device and simplify the device. A composite sensor 84 housed in one package is used. However, the use of the integrated composite sensor 84 may cause the following problem.

For example, when the incident position of the S-polarized light component on the light-receiving element 84B shifts, the light-receiving element 84B is fixed to the composite sensor 84. It becomes difficult.

An object of the present invention is to eliminate such a drawback, and to use a composite sensor for detecting two polarization components, even if a composite sensor is used to detect the two polarization components. It is to provide a detection system.

[0010]

In order to achieve the object, the present invention provides a condenser lens for condensing a light beam reflected from an optical disk, and converts the light beam from the condenser lens into first and second polarization components. A polarization beam splitter that separates and emits these first and second polarization components from the first and second exit end faces, respectively, and a second polarization component that exits from the second exit end face of the polarization beam splitter Is provided movably with respect to the second emission end face, and the incident second polarization component is reflected by the first and second mirror surfaces, and is emitted from the polarization beam splitter. A reflecting prism that emits light in the same direction as the first polarized light component, and a first polarized light component from the polarizing beam splitter and a second polarized light component from the reflecting prism are received, respectively. And first and second light receiving elements each divided surface is divided light receiving surface into a plurality to generate an output according to the focus error detection by the polarization component of the received light of,
The first and second light receiving elements are housed in one package.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.

FIG. 1 shows an embodiment of a signal detection system of an optical disk device according to the present invention. The signal detection system of the optical disk device includes a light source unit 10, a prism block 20, a light receiving element 30, an objective optical system 40, a signal detection unit 50, and a processing unit 60.

The light source unit 10 includes a semiconductor laser 11 that generates a divergent light beam, a collimator lens 12 that converts the divergent light beam from the semiconductor laser 11 into a parallel light beam, and an anamorphic prism 13 that shapes the shape of the light beam from the collimator lens 12. It has.

The prism block 20 shapes the light beam from the anamorphic prism 13 to make the cross-section of the light beam circular, a half mirror prism 22 joined to the anamorphic prism 21, and a condenser lens. 23.

The bonding surface between the anamorphic prism 21 and the half mirror prism 22 is the half mirror surface 2
2A, the anamorphic prism 2
A part of the light beam from 1 passes through the half mirror surface 22A of the half mirror prism 22 and enters the objective optical system 40.

A part of the light beam from the light source unit 10 is reflected by the half mirror surface 22A and is condensed on the light receiving element 30 by the condenser lens 23. The light receiving element 30 converts the incident light flux and generates a signal for automatic output adjustment of the semiconductor laser 11.

The objective optical system 40 includes a start-up routine prism 4 for reflecting the light beam from the half mirror prism 22.
1 and an objective lens 42 for converging the light beam from the startup routine prism 41 to the optical disc 1.

The objective lens 42 is provided in a head (not shown) that slides in the radial direction X of the optical disk 1 together with the rising routine prism 41. Also,
The objective lens 42 is provided on an actuator (not shown) in the head, and is driven in the optical axis direction Z and the radial direction X of the disk.

The reflected light from the optical disk 1 passes through the objective lens 42 and is reflected by the start-up routine prism 41.
Further, the half mirror surface 22 of the half mirror prism 22
A is reflected by the mirror surface 22B and enters the signal detection unit 50.

The signal detecting section 50 includes a condenser lens 51 for converging the light beam from the half mirror prism 22 and a PBS.
Prism 52, reflection prism 53, composite sensor 5
4 is provided.

As shown in FIG. 2, the PBS prism 52 separates the condensed light beam from the condensing lens 51 into a P-polarized light component and an S-polarized light component whose polarization angles are orthogonal to each other by a polarization plane 52A. Then, the P-polarized light component is emitted from the emission end face 52B toward the composite sensor 54, and the S-polarized light component is emitted from the emission end face 52C toward the reflection prism 53. The emission optical axis of the P polarization component at this time is the optical axis 101.

The reflecting prism 53 has an incident end face 53A.
Are opposed to the emission end face 52C of the PBS prism 52, and the incidence end face 53A is provided so as to be movable in a direction parallel to the emission end face 52C, that is, in directions 201 and 202.
The reflection prism 53 reflects the S-polarized light component from the PBS prism 52 on the mirror surface 53B, further reflects on the mirror surface 53C, and outputs the composite sensor 54 from the exit end surface 53D.
Inject toward The emission optical axis of the S-polarized component at this time is the optical axis 102. Then, the reflection prism 53 emits the S-polarized light component such that the optical axis 102 of the S-polarized light component is substantially parallel to the optical axis 101 of the P-polarized light component emitted from the PBS prism 52.

The exit end face 52 of the PBS prism 52
The positional relationship between the P-polarized light component emitted from B and the S-polarized light component emitted from the emission end face 53D of the reflection prism 53 is as follows.
It looks like this: That is, as shown in FIG. 3A, the optical axis 101 of the P-polarized light component emitted from the PBS prism 52 and the optical axis 102 of the S-polarized light component emitted from the reflection prism 53 correspond to the surface of the optical disc 1. Direction 203
When the reflection prism 53 is on a straight line parallel to
It is at a predetermined position with respect to the S prism 52. Note that P, S
The optical axes 101 and 102 of the polarization components are perpendicular to the paper surface of FIG. 3, and the P and S polarization components are emitted from the back side of the paper surface to the front side.

As described above, in order to position the optical axis 101 and the optical axis 102 on a straight line parallel to the plate surface direction of the optical disk 1, the PBS prism 52 and the reflection prism 53
Each is provided to be inclined about the optical axis 101 and the optical axis 102. Thus, as in the prior art, λ / 2
There is no need to use boards.

The reflecting prism 53 is moved from the predetermined position in the direction 20.
When moved to 1, the S-polarized component becomes the mirror surface 53B,
Since the positions reflected by 53C move respectively, FIG.
As shown in (B), the optical axis 102 of the S-polarized light component has a direction 204 perpendicular to the plate surface direction 203 of the optical disc 1.
To + ΔY. The direction 204 is the same direction as the optical axis direction Z in FIG. Also, as shown in FIG. 3C, when the reflecting prism 53 is moved in the direction 202,
The optical axis 102 of the S-polarized component moves in a direction opposite to the direction 204, that is, by −ΔY.

As described above, the reflection prism 53 moves in the direction 20.
When the optical axis 102 is moved to the position 1, 202, the optical axis 102 of the S-polarized light component emitted from the reflection prism 53 moves in the direction 204 or the opposite direction.

The composite sensor 54 includes a PBS prism 5
2. It has light receiving elements 54A and 54B for respectively receiving the P and S polarized components from the reflecting prism 53 and converting them into electric signals, and accommodates the two light receiving elements 54A and 54B in one package. Then, each light receiving element 54A,
Reference numeral 54B is arranged as shown in FIG. 4 with respect to the PBS prism 52 and the reflection prism 53 in order to receive the P and S polarization components.

At this time, the P-polarized light component from the PBS prism 52 is converged by the condenser lens 51 behind the light receiving element 54A. The S-polarized light component from the reflecting prism 53 is
Since the optical path length from the condenser lens 51 to the light receiving element 54B is longer than the optical path length of the P-polarized light component, the light is converged on the front surface of the light receiving element 54B and then enters the light receiving element 54B.

The light receiving surface of the light receiving element 54A is divided into three parallel parts as shown in FIG. The light receiving element 54
The division of the light receiving surface of A is not limited to three.
When the light receiving element 54A receives the P-polarized light component from the PBS prism 52 on the divided surfaces A1, A2, A3, the output a
1, a2 and a3, respectively.

Similarly, the light receiving surface of the light receiving element 54B is also divided into three parallel parts. When the light receiving element 54B receives the S-polarized light component from the reflecting prism 53 on the divided surfaces B1, B2, and B3, the outputs b1, b2 , B3.

At this time, the size of the spot of the light beam incident on the light receiving elements 54A and 54B is as shown in FIG. 5A when the objective lens 42 is approaching the optical disk 1, and when the objective lens 42 is in focus. , FIG. 5 (B), and
When the objective lens 42 is far from the optical disc 1, FIG.
(C).

The processing section 60 calculates the outputs a1, a2, a3 and the outputs b1, b2, b3 from the composite sensor 54 to generate a focus error signal FE. That is,
The focus error signal FE is given by the following equation.

[0033]

FE = (a1 + a3 + b2)-(a2 + b1 + b3) This focus error signal FE is output to a reproducing circuit and a servo circuit (not shown).

The detection of the focus error signal FE is as follows.
As shown in FIG. 5B, it is necessary to precisely adjust the incident positions of the P and S polarized light beams incident on the light receiving elements 54A and 54B.
It is difficult to adjust the position of the composite sensor housed in one package, and in most cases, one light-receiving element matches but the other is out of alignment.

According to this embodiment, as shown in FIG.
When the spot of the S-polarized light component incident on the light receiving element 54B is shifted by + ΔY in the optical axis direction Z, even if the light beam incident on the optical disc 1 is in a focused state, the focus error signal FE represented by Expression 1 is Does not become zero.

At this time, as shown in FIG. 3C, when the reflecting prism 53 is moved in the direction 202, the light receiving element 54 is moved.
The position of the spot on B can be moved and adjusted without moving the spot on the light receiving element 54A, and becomes the same state as the spot on the light receiving element 54A, the focus error signal FE becomes zero, and the focus error signal FE becomes zero. Output is correct.

The spot on the light receiving element 54B is -Δ
By performing the adjustment shown in FIG. 3B even when moving by Y, malfunction of the servo circuit is prevented.

[0038]

As described above, according to this invention, since the incident end face of the reflecting prism on which the second polarized light component from the polarizing beam splitter is incident is provided so as to be movable, the polarized light with respect to the light receiving element is provided. Even when the incident position of the component is shifted, the position at which the polarized component enters the light receiving element can be adjusted by moving the reflecting prism, so that the position of the composite sensor with respect to the incident polarized component can be easily adjusted.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

FIG. 2 is a diagram illustrating a reflection prism and a PBS prism of FIG. 1;

FIG. 3 is a diagram illustrating movement of a light beam emitted when the reflection prism of FIG. 1 is moved.

FIG. 4 is a diagram illustrating an arrangement of a condenser lens, a PBS prism, a reflection prism, and a composite sensor of FIG. 1;

FIG. 5 is a diagram showing a position of a spot of a light beam incident on the composite sensor of FIG. 1;

FIG. 6 is a diagram for explaining positioning of the composite sensor of FIG. 1;

FIG. 7 is a diagram illustrating an example of a signal detection unit used in a signal detection system of a conventional optical disc device.

[Explanation of symbols]

 52 PBS prism 52B Exit end face 52C Exit end face 53 Reflection prism 53A Incident end face

Claims (1)

(57) [Scope of request for utility model registration] 1. A condensing lens for condensing a light beam reflected from an optical disk, and a light beam from the condensing lens is separated into first and second polarized light components, and these first and second polarized light components are separated. The first
A polarizing beam splitter that emits light from a second exit end face, and an incident end face on which a second polarization component emitted from a second exit end face of the polarization beam splitter enters moves relative to the second exit end face. A reflecting prism that is provided so as to be able to reflect the incident second polarization component on the first and second mirror surfaces and emit the same in the same direction as the first polarization component emitted from the polarization beam splitter; A first polarization component from the polarization beam splitter and a second polarization component from the reflection prism are respectively received, and each light receiving surface is divided into a plurality of portions, and a focus error is detected by a polarization component received by each divided surface. A signal detection system of an optical disc device, comprising: a first and a second light receiving element for generating an output according to the above.