JPH05205338A - Signal detecting system for optical disk device - Google Patents

Abstract

PURPOSE:To prevent a processing part from complicating by housing 1st and 2nd light receiving elements for detecting a servo error and 3rd and 4th light receiving elements for detecting an information signal into one package. CONSTITUTION:A divergent light beam from a semiconductor laser 11 of a light source part 10 is passed through a collimator lens 12, an anamorphic (ANP) prism 13, a rectangular prism 22 coupled with an ANP 21 and a routine prism 23, and is reflected by a routine prism 31 in an objective optical system 30, and is imaged on an optical disk 1 after passing through an objective lens 32. This reflecting light is traveled reversely and reflected by the prism 22, and is made incident upon a composite sensor 44 via a condenser lens 41, a Wollaston prism 42 and a PBS prism 43 in a signal detecting system 40. Four light beams from the prism 43 are made incident upon the light receiving elements 44A-44D of the sensor 44, and their output signals are processed by the processing part 50, so that a focus error signal, a track error signal, a preformat signal and a magneto-optical recording signal are outputted.

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 device for separating a signal related to servo error detection and a signal related to information signal detection from a reflected light flux 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 the light flux reflected by the optical disc, guiding it to a light receiving element for error detection, and calculating a signal from each divided area of the light receiving element.

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

FIG. 10 shows an example of a light receiving element and a processing unit used in a signal detection system of an optical disk device by the spot size method. The light-receiving surfaces of the two light-receiving elements 81 and 82 are each divided into three parts in parallel. Then, when the reflected light beam from the optical disc is split into two by a prism block (not shown) and is incident on the light receiving elements 81 and 82, the light receiving elements 81 and 82 are split into the split surfaces 81A, 81B, and 8.
The light received by 1C and the split surfaces 82A, 82B, 82C is converted into an electric signal.

A processing unit 90 for processing the outputs from the light receiving elements 81 and 82 has an adder circuit 91 to 97 and a subtractor circuit 98 to.
100, a magneto-optical recording signal MO recorded on the optical disc, a pre-format signal RO recorded by physical unevenness, a focus error signal FE, and a track error signal TE are generated, and a reproducing circuit (not shown) is generated. Output to servo circuit.

These light receiving elements 81 and 82 and the processing section 90
Thus, the signal detection system of the conventional optical disk device generates the above four signals by comparing the sizes of the spots formed on the respective light receiving elements.

A signal detection system for an optical disk device based on the spot size method is disclosed in, for example, Japanese Patent Laid-Open No. 62-264444.

[0008]

By the way, in the signal detection system of the conventional optical disk device, as shown in FIG. 10, the processing unit 90 uses the outputs from the light receiving elements 81 and 82 to perform magneto-optical recording for information reproduction. The signal MO and the preformat signal RO are generated, and the focus error signal FE and the track error signal TE related to error detection are generated.

As described above, the signal detection system of the conventional optical disk device has a drawback that the configuration of the processing section 90 becomes complicated because four signals are generated by using the two light receiving elements 81 and 82.

Further, the signal detection system of the conventional optical disk apparatus uses a low frequency signal for error detection and a high frequency signal for information signal detection, and a circuit of a processing unit for separating these signals is used. It has the drawback of being complicated.

An object of the present invention is to provide a signal detection system for an optical disk device, which eliminates such drawbacks and prevents the structure of the processing section from becoming complicated.

[0012]

In order to achieve the object, the present invention separates a reflected light beam from an optical disc into two light beams having a polarization direction different from that of the light beam, and a light beam from the separation device. A polarization beam splitter that separates a light beam having a polarization direction that is the same as the polarization direction of the reflected light beam from the optical disc and a light beam that has a polarization direction orthogonal to this polarization direction, and receives two light beams from the polarization beam splitter. , The first and second light receiving elements that generate an output related to servo error detection by the light received by each of the light receiving surfaces, and the remaining two light beams from the polarization beam splitter, respectively. Third and fourth light receiving elements that receive light and generate outputs related to information signal detection, outputs of the first light receiving element and outputs of the second light receiving element The focus error signal and the track error signal are generated by calculating the sum and difference, and the preformat signal and the magneto-optical recording signal are calculated by calculating the sum and difference between the third light receiving element and the fourth light receiving element. And a processing unit for generating each, and the first, second, third, and fourth light receiving elements are housed in one package.

[0013]

Embodiments of the present invention will now be described with reference to the drawings.

[Embodiment 1] FIG. 1 shows Embodiment 1 of a signal detection system of an optical disk device according to the present invention. The signal detection system of this optical disc device is based on the light source unit 10.
The prism block 20, the objective optical system 30, the signal detection system 40, and the processing unit 50.

The light source unit 10 includes a semiconductor laser 11 for generating a divergent light beam, a collimator lens 12 for converting the divergent light beam from the semiconductor laser 11 into a parallel light beam, and an anamorphic prism 13 for shaping the shape of the light beam from the collimator lens 12. Is equipped with.

The prism block 20 shapes the shape of the light beam from the anamorphic prism 13 to make the cross section of the light beam circular, and a right-angle prism 22 joined to the anamorphic prism 21.
And a first routine prism 23 and a condenser lens 24.

The bonding surface of the anamorphic prism 21 and the right-angled prism 22 is formed as a half mirror surface 22A, and the light flux from the anamorphic prism 21 passes through the half-mirror surface 22A of the right-angled prism 22 to form a first mirror surface. It enters the routine prism 23.

The first routine prism 23 reflects the light beam from the rectangular prism 22 toward the objective optical system 30.

The light flux from the light source section 10 is reflected by the half mirror surface 22A and is condensed by the condenser lens 24 on the light receiving element 70. The light receiving element 70 converts the incident light flux and generates a signal for automatic output adjustment of the semiconductor laser 11.

The objective optical system 30 is a rising routine prism 3 that reflects the light beam from the first routine prism 23.
1 and an objective lens 32 that converges the light flux from the rising routine prism 31 onto the optical disc 1.

The objective lens 32 is provided in a head (not shown) that is slid in the radial direction X of the optical disc 1 together with the rising routine prism 31. Also,
The objective lens 32 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 32, is reflected by the rising routine prism 31 and the first routine prism 23, and is further reflected by the half mirror surface 22A of the rectangular prism 22 to the signal detection system 40. Incident.

The signal detection system 40 includes a prism block 20.
It includes a condenser lens 41 for converging the light flux from the, a Wollaston prism 42, a polarization beam splitter prism (PBS prism) 43, and a composite sensor 44.

The Wollaston prism 42 is a crystalline polarization element and, as shown in FIG. 2, decomposes the light flux from the condenser lens 41 into two polarization components. At this time, the Wollaston prism 42 separates the light flux in the polarization direction 101 from the condenser lens 41 into a light flux in the polarization direction 102 and a light flux in the polarization direction 103, and emits the light from the emission end face 42A. The polarization directions 102 and 103 of the light flux emitted from the exit end face 42A are the polarization directions 101 of the incident light flux.
They are inclined with respect to each other. In order to obtain the light fluxes of the tilted polarization directions 102 and 103, the Wollaston prism 42 is rotated on the optical axis of the condenser lens 41 by a predetermined angle and is placed on the optical axis of the condenser lens 41. It is arranged.

In this embodiment, the light flux reflected from the optical disk is condensed by the condenser lens 41 and the Wollaston prism 4.
Although the light is incident in the order of 2, the positions of the condenser lens 41 and the Wollaston prism 42 may be exchanged, and the reflected light flux may be incident in the order of the Wollaston prism 42 and the condenser lens 41.

As shown in FIG. 3, the PBS prism 43 separates the light beams emitted from the emission end face 42 A of the Wollaston prism 42 into two and emits them to the composite sensor 44. That is, the light flux in the polarization direction 102 from the exit end face 42A is separated into a light flux in the polarization direction 104 orthogonal to the polarization direction 101 and a light flux in the polarization direction 106 in the same direction as the polarization direction 101, and is emitted to the composite sensor 44. .. Similarly, the light flux of the polarization direction 103 emitted from the emission end face 42A is separated into the light fluxes of the polarization directions 105 and 107 and emitted to the composite sensor 44.

The composite sensor 44 is a PBS prism 43.
The light receiving elements 44A, 44B, 44C and 44D for receiving the four light fluxes from the respective and converting them into electric signals are provided.
One light receiving element 44A, 44B, 44C, 44D is housed in one package. Then, each light receiving element receives the light flux from the PBS prism 43,
It is arranged as shown in FIG.

The light receiving element 44A is related to information signal detection. Then, the light receiving element 44A generates an output a when the light beam in the polarization direction 104 from the PBS prism 43 is received on the light receiving surface as an S-polarized light beam.

The light receiving element 44B is related to servo error detection, and the light receiving surface of the light receiving element 44B is divided into three parallel parts. The light receiving surface of the light receiving element 44B is divided into
It is not limited to three divisions. This light receiving element 44B
When the light beams of the polarization direction 106 from the PBS prism 43 are received as P-polarized light beams on the split surfaces B1, B2, B3, outputs b1, b2, b3 are generated, respectively.

Similarly, the light receiving element 44C also relates to servo error detection and is divided into three parallel parts. When the light receiving element 44C receives the light beam with the polarization direction 105 as the S-polarized light beam on the split surfaces C1, C2, C3, the output c
1, c2, c3 are generated.

Further, the light receiving element 44D relates to information signal detection, and the light receiving element 44D has a polarization direction of 10
The light flux of No. 7 is received as a P-polarized light flux and an output d is generated.

At this time, the positions of the spots of the light beams incident on the light receiving elements 44B and 44C are as shown in FIG. 9A when the objective lens 32 is close to the optical disk, and when the in-focus state is achieved, 9 (B), and when the objective lens 32 is far from the optical disc, it becomes as shown in FIG. 9 (C).

In this embodiment, the light receiving elements are arranged as shown in FIG. 4, but the arrangement is not particularly limited to this, and the arrangements shown in FIGS. .. In FIG. 5, the light-receiving surfaces of the light-receiving elements 44A and 44D of FIG. 4 are divided into three parallel parts for servo error detection, and the light-receiving surfaces of the light-receiving elements 44B and 44C are not divided for information signal detection. Further, in FIG. 6, the light receiving elements 44C and 44
The light receiving surface of D is divided for servo error detection, and the light receiving surfaces of the light receiving elements 44A and 44B are not divided for information signal detection.

As shown in FIG. 7, the processing section 50 includes addition circuits 51 to 55 and subtraction circuits 56 to 58.

The adder circuit 51 outputs the output c1 when the light is received by the split surface C1 of the light receiving element 44C, the output c3 when the light is received by the split surface C3, and the output b2 when the light is received by the split surface B2 of the light receiving element 44B. And the sum is calculated and sent to the subtraction circuit 57.

The adder circuit 52 outputs the output c of the light receiving element 44C.
2 and the outputs b1 and b3 of the light receiving element 44B are calculated and sent to the subtraction circuit 57.

The subtractor circuit 57 calculates the difference between the outputs from the adder circuits 51 and 52 to generate the focus error signal FE. That is, the focus error signal FE is given by the following equation.

[0038]

FE = (c1 + c3 + b2)-(c2 + b1 + b3) Similarly, the track error signal TE is added by the adder circuit 5
3 and 54 and the subtraction circuit 58 give the following formula.

[0039]

## EQU2 ## TE = (c1 + b3)-(c3 + b1) The preformat signal RO is given by the addition circuit 55 by the following equation.

[0040]

## EQU3 ## RO = d + a The magneto-optical recording signal MO is given by the subtraction circuit 56 by the following equation.

[0041]

MO = d−a These focus error signal FE, track error signal TE, preformat signal RO, magneto-optical recording signal M
O is output to a reproduction circuit and a servo circuit (not shown).

In the first embodiment, the Wollaston prism 42 and the PBS prism 43 are used to separate the reflected light beam from the optical disk 1 into four, and the composite sensor 44 receives the four separated light beams. Since it is converted into an electric signal by the processing unit 50, the processing unit 50 does not need the addition circuit 97 and the subtraction circuit 98 of the conventional processing unit 90 shown in FIG. Further, the first embodiment has four light receiving elements 44A.
Since 44D are used, the processing unit 50 can connect the respective light receiving elements and the respective adding circuits more easily than in the conventional case. Furthermore, since the four light receiving elements 44A to 44D are housed in one package, compared with the signal detection system of the conventional optical disk device using two light receiving elements,
The shape of the light receiving element can be reduced.

[Embodiment 2] FIG. 8 shows Embodiment 2 of the signal detection system of the optical disk device according to the present invention.

In the second embodiment, a prism block 60 is used instead of the prism block 20 of the first embodiment.
The bonding surface of the anamorphic prism 61 and the rectangular prism 62 of the prism block 60 is formed as a half mirror surface 62A. Then, the light flux from the light source unit 10 is shaped into a circular cross section by the anamorphic prism 61 and is incident on the half mirror surface 62A.

The luminous flux transmitted through the half mirror surface 62A is
It is incident on the objective optical system 30. The reflected light flux from the optical disk 1 is reflected by the half mirror surface 62A of the rectangular prism 62 and enters the signal detection system 40.

The light flux from the light source unit 10 is reflected by the half mirror surface 62A and is condensed on the light receiving element 70 by the condenser lens 63. The light receiving element 70 converts the incident light flux and generates a signal for automatic output adjustment of the semiconductor laser 11.

[0047]

As described above, according to the present invention, since the four light receiving elements are integrated, the shape of the light receiving element can be reduced. Further, since four light receiving elements are used, there is an effect that the configuration of the processing unit can be simplified as compared with the signal detection system of the conventional optical disk device.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a first embodiment of the present invention.

FIG. 2 is a diagram for explaining a signal detection system.

FIG. 3 is a diagram for explaining separation of a light beam by a PBS prism.

FIG. 4 is a diagram showing an example of arrangement of light receiving elements of a composite sensor.

FIG. 5 is a diagram showing another example of arrangement of light receiving elements of a composite sensor.

FIG. 6 is a diagram showing another example of arrangement of light receiving elements of a composite sensor.

FIG. 7 is a diagram for explaining a light receiving element and a processing unit.

FIG. 8 is a diagram for explaining a second embodiment of the present invention.

FIG. 9 is a diagram showing positions of spots of a light beam incident on a composite sensor.

FIG. 10 is a diagram for explaining a light receiving element and a processing unit of a signal detection system of a conventional optical disc device.

[Explanation of symbols]

 1 Optical Disc 42 Wollaston Prism 43 PBS Prism 44A Photoreceptor 44B Photoreceptor 44C Photoreceptor 44D Photoreceptor

Claims (4)

[Claims] 1. A separating means for separating a reflected light beam from an optical disc into two light beams having a polarization direction different from that of the light beam, and each of the light beams from the separating device has the same polarization direction as that of the reflected light beam from the optical disc. And a polarization beam splitter that separates a light beam of a polarization direction orthogonal to this polarization direction, and two light beams from the polarization beam splitter, respectively, and each light receiving surface is divided into a plurality of light beams. First and second light receiving elements that generate an output related to servo error detection by the light received by the split surface, and the remaining two light beams from the polarization beam splitter are respectively received, and an output related to information signal detection is obtained. The third and fourth light-receiving elements to be generated, and the sum and difference of each output of the first light-receiving element and each output of the second light-receiving element are calculated. A processing unit that generates a focus error signal and a track error signal, calculates the sum and difference of the third light receiving element and the fourth light receiving element, and generates a preformatted signal and a magneto-optical recording signal, respectively. A signal detection system for an optical disk device, comprising: the first, second, third, and fourth light-receiving elements in one package. 2. The separating means comprises a condenser lens for condensing a reflected light beam from the optical disc, and a crystalline polarizing element for separating the light beam from the condensing lens into two light beams having polarization directions different from the light beam. The signal detection system of the optical disk device according to claim 1, further comprising: 3. The crystalline polarization element for separating the reflected light beam from the optical disc into two light beams having a polarization direction different from this light beam, and a condenser lens for condensing the light beam from the crystalline light polarization element. The signal detection system of the optical disk device according to claim 1, further comprising: 4. The signal detection system for an optical disk device according to claim 2, wherein the crystalline polarization element is a Wollaston prism.