JP3214531B2 - Optical information reproducing method and apparatus therefor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for reproducing information by irradiating an optical information recording medium such as an optical disk with a light beam to reproduce information.

[0002]

2. Description of the Related Art Conventionally, in an optical disk device, as disclosed in Japanese Patent Application Laid-Open No. 1-245433 and the like, light emitted from a semiconductor laser is narrowed down to one point of an optical medium using an optical system and irradiated. Reflected light from one point is collected by the optical system, guided to a light detector, and changes in the light intensity and the polarization direction of the reflected light are captured on the light detector, and a signal recorded at one point is reproduced.

In addition, next-generation optical head technology for magneto-optical recording (Applied Physics Vol. 61, No. 3 (1992), pp. 258-26)
As disclosed in (1), as a high-density technology, a minute spot exceeding a diffraction limit is formed on a recording medium by using a super-resolution optical technology in addition to a semiconductor laser.

In this next-generation optical head technology, as shown in FIG. 2, a laser beam emitted from a semiconductor laser 101 is shaped by passing through a beam shaping prism 102, and then the laser beam is passed through a light-shielding band 103 for forming a super-resolution spot. By irradiating the recording medium 104 with light, a minute spot exceeding the diffraction limit is formed on the recording medium 104. On this occasion,
Extraction of the reflected light from the recording medium 104 to the error detection system 105 and the signal detection system 106 is performed by the beam splitters 108 and 1 disposed between the light-shielding band 103 and the objective lens 107.
09, and the error signal is detected by a general knife edge method and a push-pull method. Further, in the signal detection system 106, a spot is formed on the slit surface to transmit only the main lobe component, and after the polarization separation, the signal is differentially detected by the photodetector.

With the above-described configuration, the light source wavelength is set to 780n.
When a condenser lens having an NA of 0.55 and m is used, the beam diameter is reduced from 1.4 μm to 1.1 μm, and the frequency characteristic is improved by about 20% correspondingly.

[0006]

However, in the above-described optical information reproducing apparatus using the conventional optical head, the intensity of reflected light and the like are detected by one optical detector.
Since the signal detection system was also used only to suppress the influence of unnecessary side lobes, the state in the spot formed on the optical medium having the reproduction beam could not be detected,
The reproduction of minute pits was not possible. Furthermore, since the above-described method using the next-generation optical head technology generates side lobes, a slit is provided in the signal detection system in order to suppress the side lobes, so that the light use efficiency has been reduced.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical information reproducing method and an apparatus thereof having improved resolution and utilization efficiency in view of the above problems.

[0008]

In order to achieve the above object, according to the present invention, there is provided an optical information reproducing apparatus for reproducing information of a recording mark formed on an information recording medium by using a light beam. in the reproducing method, wherein a light beam is irradiated onto the information recording medium, before the light returning from the information recording medium
The light beam on the information recording medium is spatially divided into three or more regions in the traveling direction of the light beam , and the divided lights are respectively condensed and divided into a central region and another region to provide separate detectors.
Or with a separate detector for each region ,
An optical information reproducing method for reproducing the information of the recording mark by weighting and calculating each of the outputs of the plurality of detectors is proposed.

According to a second aspect of the present invention, in the optical information reproducing method according to the first aspect, the divided area of the light is divided into the information recording medium.
An optical information reproducing method is proposed which corresponds to the shape of the first-order diffracted light from the recording mark on the body .

According to a third aspect, in the optical information reproducing method according to the first or second aspect, the information recording medium is provided.
Part of the light passing through the half-wave plate
After that, irradiate the polarizing beam splitter with other parts
Optical information reproduction method that spatially divides
You.

Further, in claim 4, claim 1 or claim
Item 3. The optical information reproducing method according to Item 2, wherein the information recording medium is
The light returning from the body is split into two beams by a polarizing beam splitter.
And separates each of the two separated polarized light components into polarized light components.
Space in the traveling direction of the light beam on the information recording medium
Optical information reproduction method that divides into three or more regions
You.

[0012] According to claim 5, by irradiating a light beam onto the information recording medium in the optical information reproducing apparatus for reproducing information of a recording mark formed on the information recording medium, returning from the information recording medium Light on the information recording medium
Light dividing element that spatially divides the light beam into three or more regions in the traveling direction of the light beam, and separately detects the light divided by the light dividing element into a central region and other regions.
Or a plurality of detection means for detecting separately for each region ,
We propose an optical information reproducing apparatus provided with a calculation means for calculating by weighting the output of each of said plurality of detection means.

[0013] According to claim 6, in the optical information reproducing apparatus according to claim 5, with the divided region of the light by the light splitting element to correspond to first shape of the diffracted light from the recording mark on the information recording medium The proposed optical information reproducing device is proposed.

In claim 7, claim 5 or claim 5
Item 7. The optical information reproducing apparatus according to Item 6, wherein the light splitting element
Passes a part of the light returned from the information recording medium.
Half-wave plate and polarizing beam splitter
And the light passing through the half-wave plate is transmitted to another part.
Irradiating the polarized beam splitter with the light of the minute
Spatially divides the light returned from the information recording medium
Optical information reproducing apparatus is proposed.

In claim 8, claim 5 or claim 5
Item 7. The optical information reproducing apparatus according to Item 6, wherein the information recording medium is
Polarization beam that separates the light returned from
And a polarizing beam splitter.
The light for each of the two polarization components separated by
An optical information reproducing apparatus provided with a splitting element and the plurality of detectors;
suggest.

[0016]

According to the optical information reproducing method of the first aspect of the present invention, the information recording medium is irradiated with the light beam, and the light returned from the information recording medium is reflected on the information recording medium.
Is divided into spatially three or more regions in the traveling direction of the beam, the traveling direction of the aberration of the light beam is Ru is corrected. further,
After each of the divided light is collected, the central area and its
Detect with separate detector separately from other areas or
Each region is detected by a separate detector, and the plurality of detectors
Each of the outputs is weighted and operated, and information of a recording mark formed on the information recording medium is reproduced.
For example, light is spatially divided into a portion having many signal components from a recording mark and another portion, and in the calculation, a detection signal of another portion is subtracted from a detection signal of a portion of the recording mark. This suppresses effects other than noise and signal components of recording marks.

According to a second aspect of the present invention, the divided area of the light corresponds to a shape of a first-order diffracted light generated from a recording mark on the information recording medium, and a signal component to be reproduced and a first-order diffracted light are formed. The components are separated.

Further , according to claim 3, the information recording medium
Part of the light returned from the body passed through the half-wave plate
After that, it is irradiated to the polarizing beam splitter together with other parts
Is divided spatially.

Further , according to claim 4, the information recording medium
Light returning from the body is split into two polarized light beams by a polarizing beam splitter.
Each of the two polarized components separated into light components
Is empty in the traveling direction of the light beam on the information recording medium.
It is intermittently divided into three or more areas.

Further, according to the optical information reproducing apparatus according to claim 5, wherein the information by light beam splitting device which has returned from the recording medium in the traveling direction of the light beam on the information recording medium <br/> spatially Divided into three or more areas, and how the light beam travels
The directional aberration is corrected. Further, the light split by the splitting element is detected by the detecting means so that the light is split into the central area and other areas.
Each area is separately detected , or separately detected for each area . Further, the plurality of detections are performed by an arithmetic unit.
The outputs of the means are weighted and calculated, and the information of the recording marks formed on the information recording medium is reproduced. For example, the light is spatially divided into a portion having a large signal component from the recording mark by the light splitting element and another portion, and the detection signal of the other portion is subtracted from the detection signal of the recording mark portion by the calculating means. . This suppresses effects other than noise and signal components of recording marks.

According to the present invention, light is divided by the light splitting element in accordance with the shape of first-order diffracted light generated from a recording mark on the information recording medium, and a signal component to be reproduced is obtained. And the first-order diffracted light component.

According to claim 7, the light splitting element
As a result, part of the light returned from the information recording medium
After passing through the half-wave plate, it passed through the half-wave plate
Both the light and the other part of the light that does not pass through the half-wave plate
Illuminates the polarizing beam splitter and is spatially split
You.

Further , according to claim 8, the information recording medium
The light returning from the body is
Separated into two polarization components, and the separated two polarization components
After each of the light beams is split by the light splitting element.
Detected by a number of detectors.

[0024]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing a first embodiment of the present invention. In the figure, 1 is an optical disk, 2 is an objective lens for forming a beam spot on the optical disk 1, 3 is a beam splitter for separating light, 4 is a beam splitting element composed of, for example, a mirror, 44 is a splitting element mounting unit, and 5 is a lens. A beam shaping unit composed of, for example, 6 a laser, 7 and 8 a condenser lens,
9 and 10 are detectors, and 11 is an arithmetic circuit.

Hereinafter, a more detailed configuration and operation of this embodiment will be described. The light output from the laser 6 is shaped into parallel light by a beam shaping unit 5, and the parallel light is applied to an objective lens 2 via a beam splitter 3 and collected on a recording layer on the optical disc 1 by the objective lens 2. Be lighted. The reflected light from the recording layer can be changed its polarization direction by the beam splitter 3 (to change the direction, a well-known quarter-wave plate may be inserted or PBS may be used). It goes to the beam splitter 4.

FIG. 3 shows a light beam splitting region at a cross section of the beam splitting element 4. As shown in the drawing, the beam cross section is divided into a first area 21, a second area 22, and a third area 23 with respect to the beam traveling direction on the medium (optical disc 1). Then, the beam splitting element 4 is inserted into the second area 22 to separate the light. A first area 21,
The light in the third area 23 is condensed on the detector 9 by the condenser lens 7. The light in the second region 22 is reflected by the beam splitting element 4 in, for example, a right angle direction, and then is collected by the condenser lens 8 on the detector 10. The outputs of the detector 9 and the detector 10 are guided to an arithmetic circuit 11 and operated.

In the arithmetic circuit 11, the output of the detector 9 is V
1. Assuming that the output of the detector 10 is V2, the output O is represented by the following equation.

O = aV1 + bV2 (1) where a and b are amplification factors, which depend on the beam splitting area shown in FIG.

As a good example, b is reduced so that aV1> bV2. A good example for improving the resolution is 0 <| bV2 / aV1 | <0.6. A good example for reducing noise is 0> bV2 / aV1.

As described above, by constructing the reproducing system, the signal from the recording mark on the optical disc 1 is converted into the first area 21 and the third area 21 as the intensity distribution of the parallel beam which is the Fourier transform surface on the optical disc 1. It appears in the region 23 as being larger than the second region 22. Therefore, by setting the amplification factors of the signals in the first area 21 and the third area 23 to be higher than the amplification rates of the signals in the second area 22, the reproduction signal of the small recording mark can be emphasized and reproduced. . Also, the noise is random, and the first to third regions 2
Considering that it appears equally to 1, 22, and 23,
From the signals in the region 21 and the third region 23 of the second region 2
By subtracting the two signals, the effect of noise can be offset.

That is, the resolution can be improved and the noise can be suppressed by utilizing the Fourier transform effect due to the light noise, and the recording mark on the optical disc 1 can be detected with high sensitivity. In addition, since the light beams are split and the light is condensed on the detectors 9 and 10 by the condensing lenses 7 and 8, high-speed photoelectric conversion can be performed.

Further, in this embodiment, the number N of beam splitting regions is set to 3 (N = 3), but the number N of beam splitting regions is set to N.
If is an integer of 4 or more, the resolution can be further improved.

Further, in this embodiment, two detectors after beam splitting are provided, one is assigned to the center area, and one is assigned to the left and right areas. By detecting the light with the detector and adjusting the amplification factor after the detection, the aberration of the light beam with respect to the optical disc 1 in the beam traveling direction can be corrected.

Although a focus signal and a tracking signal necessary for detection of an actual signal are detected from light split by a beam splitter (not shown), a well-known method can be used. Is omitted.

Next, a second embodiment of the present invention will be described.
The configuration of the apparatus according to the second embodiment is the same as that of the first embodiment, and a description thereof will be omitted. The difference between the second embodiment and the first embodiment lies in that the shape of the light beam splitting area by the beam splitting element 4 is changed.

That is, the division area of the light beam by the beam splitting element 4 in the second embodiment is, as shown in FIG. 4, compared with the division area shown in FIG. The shape of the divided area is a curve. By doing so, signals from the minute mark can be efficiently collected in the first area 31 and the third area 33, and the signal from the minute mark can be detected efficiently. Note that the first region 31 and the third region 33 may be in contact at the center.

Next, a third embodiment of the present invention will be described.
The configuration of the apparatus according to the third embodiment is the same as that of the first embodiment, and a description thereof will be omitted. The difference between the third embodiment and the first embodiment is that the shape of the light beam splitting area by the beam splitting element 4 is changed.

That is, as shown in FIG. 5, the division area of the light beam by the beam division element 4 in the third embodiment is different from the division element shown in FIG. In accordance with the decrease of, the divided shape is curved. By doing so, it is possible to suppress the influence of tracking and efficiently detect signals from minute marks.

Next, a fourth embodiment of the present invention will be described.
FIG. 6 is a configuration diagram showing a fourth embodiment of the present invention. In the figure, the same components as those of the first embodiment described above are denoted by the same reference numerals, and description thereof will be omitted. The difference between the fourth embodiment and the first embodiment is that the beam splitting element 51,
The light beam is split using the light beam 52 and each of the split light beams is condensed on the detectors 541 and 542 via the same condensing lens 53.

That is, the reflected light from the optical disk 1 reaches the splitting element mounting section 55 via the objective lens 2 and the beam splitter 3, and a part of the beam is formed by a mirror mounted on the splitting element mounting section 55. The light is reflected by the dividing element 51 in, for example, a right angle direction. The light beam of the portion not irradiated to the beam splitting element 51 is condensed by the condenser lens 53 on the detector 541 on the substrate 54, converted into an electric signal, and input to the arithmetic circuit 56.

On the other hand, the light beam reflected by the beam splitting element 51 is applied to a beam splitting element 52 composed of a mirror, and the condensing lens 5 is
3 and is reflected by the condenser lens 53 to the substrate 54.
The light is condensed on a detector 542 arranged above the detector 541. The electric signal obtained by the detector 542 is input to the arithmetic circuit 56, and is subjected to arithmetic processing with the output signal of the detector 541.

As described above, in this embodiment, the splitting element 52 is changed, and the split light is compared with the first embodiment by using the same condenser lens 53 and the detector 5 on the same substrate 54.
41,542. With this configuration, the noise characteristics of the detectors 541 and 542 are made the same, and the output signals of these detectors 541 and 542 are differentially detected by the arithmetic circuit 56 so that the detectors 541 and 5
42 can be suppressed. The light division mode at this time may be the same as that described with reference to FIGS. 3, 4, and 5.

Next, a fifth embodiment of the present invention will be described.
FIG. 7 is a configuration diagram showing a fifth embodiment of the present invention. In the figure, the same components as those of the first embodiment described above are denoted by the same reference numerals, and description thereof will be omitted. Further, the difference between the fifth embodiment and the first embodiment is that the method of division is changed in the fifth embodiment.

That is, in this embodiment, a split element mounting section 44 is provided in place of the split element mounting section 4 of the first embodiment. A half-wave plate having a shape as shown in FIGS. 3, 4, and 5 is arranged in the reproduction beam, and a polarization beam splitter 45 is mounted on the split element mounting section 44.

As a result, a part of the reflected light from the optical disk 1 passes through the half-wave plate 46 and irradiates the polarization beam splitter 45, and the light whose polarization direction has been changed by the half-wave plate 46 is changed. Only the light is reflected by the polarization beam splitter 45, and the other light is collected by the condenser lens 7 on the detector 9. In addition, the polarization beam splitter 4
The light reflected by 5 is collected on a detector 10 by a condenser lens 8.

Therefore, the light beam can be split by the half-wave plate 46 and the polarizing beam splitter 45, and the processing after the splitting is the same as in the first embodiment. Here, a light beam may be separated using a prism such as Wollaston in addition to the polarization beam splitter 45.

As in the fourth embodiment, one of the separated light beams is reflected by a mirror, and the two separated light beams are separated by two detectors arranged side by side on one substrate. It can also be focused. In this case, if a prism such as Wollaston is used, there is no need to use a mirror, which is a good example. Furthermore, the light division form at this time is
What is necessary is just to carry out similarly to what was demonstrated about FIG. 3, FIG. 4, FIG.

Next, a sixth embodiment of the present invention will be described.
Although the above-described first to fifth embodiments have shown the ROM such as a CD and the optical system of the phase change and the write-once, in the case of the magneto-optics, it can be realized as follows.

FIG. 8 is a block diagram showing a sixth embodiment of the present invention. In the present embodiment, after the reproduction light is emitted from the laser 6 and irradiates the optical disc 1, it is conventionally known until it is reflected by the optical disc 1 and reaches the deflection beam splitter 71, similarly to the first embodiment. Since it is a method, its detailed description is omitted.

In this embodiment, the polarization beam splitter 71 separates the light into two polarization components, and further divides each light into two. That is, the light of one polarization component split by the polarization beam splitter 71 passes through the polarization beam splitter 71 and goes to the splitting element mounting portion 744, and the light of the other polarization component is reflected by the polarization beam splitter 71 and split by the splitting element splitting element. It goes to the mounting part 844.

First, the light that has passed through the polarizing beam splitter 71 will be described. Here, as shown in FIG. 3, the beam cross section is
It is divided into a first area 21, a second area 22, and a third area 23. Then, the beam splitting element 74 is inserted into the second area 22 to separate the light. First and third regions 2
Lights 1 and 23 are condensed on a detector 79 by a condenser lens 77, and light in the second region 22 is condensed on a detector 710 by a condenser lens 78.

Next, the light that has been reflected by the polarization beam splitter 71 and changed direction will be described. here,
As shown in FIG. 3, the beam cross section is set to the first to third regions 21, 22 and 22 with respect to the beam traveling direction on the optical disc 1.
23. Then, the beam splitting element 84 is inserted into the second area 22 to separate the light. First area 2
The light in the first and third regions 23 is condensed on a detector 89 by a condenser lens 87, and the light in the second region 22 is condensed on a detector 810 by a condenser lens 88.

The outputs of the detector 79 and the detector 89 are subtracted by the differential amplifier 91 and input to the arithmetic circuit 93. The outputs of the detectors 710 and 810 are
The signal is subtracted by the differential amplifier 92 and input to the operation circuit 93. The operation circuit 93 receives the outputs of the differential amplifier 91 and the differential amplifier 92, and performs the same operation on them as in the first embodiment. At this time, the light may be divided as shown in FIGS. 4 and 5 in addition to FIG.

The above embodiments may be performed alone or in combination.

[0055]

As described above, according to the optical information reproducing method of the first aspect of the present invention, the light returned from the information recording medium is spatially divided, and a signal based on the divided light is converted. Since the calculation is performed, influences other than noise and signal components of the recording mark are suppressed, the resolution and the light use efficiency can be improved, and the recording mark on the information recording medium can be detected with high sensitivity. In addition, the light beam
Aberration in the direction of travel is corrected to increase resolution
Can be.

According to the second aspect , in addition to the above-described effects, the signal component to be reproduced and the first-order diffracted light component are separated, so that a signal from a minute recording mark can be efficiently detected by these calculations. can do.

According to the third aspect, in addition to the above effects, a part of the light returned from the information recording medium is reduced to a half wave.
After passing through the long plate, the polarizing beam splitter is
Divides the space spatially with a simple configuration
be able to.

According to claim 4, in addition to the above effects,
The light returned from the information recording medium is
After splitting into two polarization components with a litter, split each
Direction of the light beam on the information recording medium
Can be easily divided into three or more areas spatially
You.

[0059] Further, according to the optical information reproducing apparatus according to claim 5, wherein the light returning from the information recording medium is spatially divided by the light dividing element, the signal based on the split light is calculated In addition, it is possible to suppress the effects other than noise and signal components of the recording mark, to improve the resolution and the light use efficiency, and to detect the recording mark on the information recording medium with high sensitivity. Further, aberration in the traveling direction of the light beam is corrected, and the resolution can be further improved.

According to the present invention, in addition to the above-described effects, the signal component to be reproduced and the first-order diffracted light component are separated from each other. can do.

According to claim 7, in addition to the above effects,
In addition, half of the light returned from the information recording medium
After passing through the long plate, the polarizing beam splitter is
Divides the space spatially with a simple configuration
be able to.

According to claim 8, in addition to the above effects,
The light returned from the information recording medium is
After splitting into two polarization components with a litter, split each
Direction of the light beam on the information recording medium
Can be easily divided into three or more areas spatially
You.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a conventional example.

FIG. 3 is a diagram showing divided regions of a reproduction beam in the first embodiment of the present invention.

FIG. 4 is a diagram showing divided areas of a reproduction beam in a second embodiment of the present invention.

FIG. 5 is a diagram showing divided regions of a reproduction beam according to a third embodiment of the present invention.

FIG. 6 is a configuration diagram showing a fourth embodiment of the present invention.

FIG. 7 is a configuration diagram showing a fifth embodiment of the present invention.

FIG. 8 is a configuration diagram showing a sixth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical disk, 2 ... Objective lens, 3 ... Beam splitter, 4 ... Beam splitting element, 44 ... Splitting element mounting part, 5 ...
Beam shaping unit, 6 ... Laser, 7,8 ... Condensing lens, 9,
Reference numeral 10: detector, 11: arithmetic circuit, 51, 52: beam splitting element, 53: condenser lens, 54: substrate, 541, 54
2: detector, 55: split element mounting part, 56: arithmetic circuit,
45 ... polarizing beam splitter, 46 ... 1/2 wavelength plate, 7
DESCRIPTION OF SYMBOLS 1 ... Polarization beam splitter, 74 ... Beam splitting element, 7
44: split element mounting portion, 77, 78: condenser lens, 7
9,710 ... detector, 84 ... beam splitting element, 844 ...
Dividing element mounting part, 87, 88 ... condenser lens, 89, 81
0: detector, 91, 92: differential amplifier, 93: arithmetic circuit.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-96465 (JP, A) JP-A-4-89637 (JP, A) JP-A-1-224936 (JP, A) JP-A-2- 257474 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B ^7/ 00-7/013 G11B 7/135

Claims (8)

(57) [Claims] 1. An optical information reproducing method for reproducing information of a recording mark formed on an information recording medium by using a light beam, wherein the information recording medium is irradiated with a light beam and returned from the information recording medium. Light on the information recording medium
Three or more regions in the traveling direction of the light beam at
And split each of the split lights into a central area and other areas.
Detection with separate detectors for each area or for each area
An optical information reproducing method, wherein the information of the recording mark is reproduced by detecting with different detectors , weighing each of the outputs of the plurality of detectors and performing calculations. 2. The method according to claim 1, wherein the divided area of the light is formed on the information recording medium.
1 optical information reproducing method according to claim 1, characterized in that in correspondence to the shape of the diffracted light from the recording mark. 3. The light returned from the information recording medium,
After passing a part of the light through a half-wave plate,
Both are spatially separated by irradiating the polarizing beam splitter.
3. The method according to claim 1, wherein the dividing is performed.
Optical information reproduction method. 4. The light returned from the information recording medium,
The light is split into two polarization components by a polarization beam splitter,
Each of the two separated polarized light components is placed on the information recording medium.
Into three or more regions in the direction of travel of the light beam
3. The method according to claim 1, wherein the dividing is performed.
Optical information reproduction method. 5. An information recording medium an optical information reproducing apparatus which irradiates a light beam for reproducing information of a recording mark formed on the information recording medium, the information recording light that has returned from the information recording medium Medium
Three or more regions in the direction of travel of the light beam
A light dividing element that divides the light into two regions,
Detecting separately divided into the other region or for each of the regions
A plurality of detecting means for detecting separately, the optical information reproducing apparatus characterized in that a calculating means for to calculating the weighting to each of the outputs of said plurality of detection means. 6. A light dividing area by the light dividing element is located in front of the light dividing area.
6. The optical information reproducing apparatus according to claim 5, wherein the optical information reproducing apparatus is set so as to correspond to a shape of a first-order diffracted light from a recording mark on the information recording medium . 7. The optical splitting device according to claim 1 , wherein
1 provided to pass a part of the light returned from
A half-wave plate and a polarizing beam splitter.
The light that has passed through the two-wavelength plate and the light of the other portions are combined with the polarized light beam.
Irradiating the beam splitter from the information recording medium
It is characterized by spatially dividing the returned light
The optical information reproducing apparatus according to claim 5 or 6, wherein
Place. 8. The light returning from the information recording medium is reflected by the
Provide polarization beam splitter to separate two polarization components
And the two separated by the polarizing beam splitter
The light splitting element and the plurality of
6. The method according to claim 5, wherein a detector is provided.
7. The optical information reproducing apparatus according to 6.