JP2003067970A - Optical pickup and information recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup which can prevent drop in the light spot performance caused by the incident light oblique to the objective lens when using multi-beams. SOLUTION: In optical pickup that has a light source emitting two or more fluxes of light, a polarizing plane turn means to turn a part or all of the polarizing plane of the light source for only a predetermined angle, and an objective lens to condense the light from the light source on an information recording medium, this invention is characterized in that the spot intensity P1 and P2...Pn condensed on the information recording medium have the following relations for the polarizing plane turn angle of the beam irradiated to the above objective lens θ1, θ2...θn (n>2). P1>P2>...>Pn...(1) or P1<P2...<Pn...(2).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup device and an information recording / reproducing device, and more particularly to an optical pickup device using a multi-beam.

[0002]

2. Description of the Related Art An optical pickup device is known as a device for recording information on an information recording medium and reproducing the recorded information. In the information recording / reproducing system using the optical pickup device, first, the spot of the light flux for performing the recording by accessing is positioned at a desired address,
After that, recording is performed, and then confirmation reproduction is performed to confirm (verify) whether the recording is completed. In this way, in addition to the original recording, the recording of information is performed by a verifying operation called verification, which requires a long time.

In order to solve such a problem, a multi-beam optical pickup device has been proposed (for example, Japanese Patent No. 2644251, Japanese Patent No. 2651454, Japanese Patent Laid-Open No. 9-312035, Japanese Patent Laid-Open No. 7-326064, Japanese Patent No. 3079075, JP-A-10-14390.
8 publication). In the pickups disclosed in these publications, for example, in FIG. 15 showing the configuration disclosed in Japanese Patent Laid-Open No. 9-312035, a laser beam emitted from a semiconductor laser LD having two light emitting points is grating GR, The information beam is guided to the information recording medium P by being condensed by the objective lens OR via the half mirror HM, and the reflected beam from the information recording medium P is transmitted to the polarization beam splitter PBS via the half mirror HM to the light receiving element PD. It's coming. in this way,
In each of the above publications, a semiconductor laser having two light emitting points is used, two light fluxes from these light emitting points are guided to the same objective lens, and are condensed on the same track on the optical information recording medium by the objective lens. At the time of recording, information is recorded by the preceding light flux and reproduction for confirmation is performed by the following light flux. By doing so, the result of recording by the preceding light flux can be immediately confirmed and reproduced by the subsequent light flux, and therefore the processing time can be greatly shortened.

[0004]

However, the optical pickup device adopting the multi-beam system having two light emitting points has the following problems. First, there is wavefront deterioration due to obliquely incident light emitted from the light emitting point. That is, in the multi-beam optical pickup, as described above, the light beams from the two light emitting points of the semiconductor laser are guided to the same objective lens, and are condensed on the same track on the optical information recording medium via the objective lens. . As an example thereof, there is the above-mentioned conventional technique. However, the two light beams enter the objective lens at different angles. If such an oblique incidence is performed, the wave performance is deteriorated and the spot performance on the board cannot be secured. In particular, the higher the NA of the objective lens, the greater the deterioration. When tilted light enters the objective lens, the coma aberration deteriorates the spot shape and the recording / reproducing performance is deteriorated.

Secondly, it is difficult to separate the light source monitor beam. That is, in the optical pickup device, it is important that the amount of light emitted from the laser light source is stable in order to stably detect various information or perform stable recording operation. Therefore, conventionally, the amount of light emitted from the laser light source is monitored by a monitor light receiving element, and the amount of light emitted from the laser light source is controlled according to the amount of light received by the monitor. In this case, the monitoring method is
Some laser light source chips have a built-in monitor light-receiving element that receives backward light emitted toward the rear, but the structure of the laser light source is restricted, and it corresponds to the front light actually used. However, it is not always accurate, and it is common to provide a monitor light receiving element that receives a part of the light beam emitted forward from the laser light source. FIG. 16 shows an example thereof. However, in the multi-beam optical system as in the prior art, two light beams enter the light receiving element at the same time, and independent control of each laser light source becomes impossible.

Thirdly, it is difficult to separate the servo signal detecting beam. That is, in the multi-beam method, the intervals between the light spots are narrow, and as a result, similar to the problem 2, the light spots from the two laser chips may be simultaneously irradiated onto the light receiving element. In this case, the focus signal, There arises a problem that the track signal and the information reproduction signal cannot be accurately detected.

The present invention has been made in view of the above problems in the conventional optical pickup device. As a first object, deterioration of spot performance due to oblique incidence of light on an objective lens when using a multi-beam is prevented. An object of the present invention is to provide an optical pickup device having a configuration capable of performing.

A second object of the present invention is to provide an optical pickup device having a structure capable of performing monitor control of each light source when multi-beams are used while maintaining high reliability.

A third object of the present invention is to provide an optical pickup device having a structure capable of highly reliable detection of a servo progress detection beam at each light source when using a multi-beam. It is in.

A fourth object of the present invention is to provide an optical pickup device having a structure capable of ensuring the power of a recording beam with improved light utilization efficiency.

A fifth object of the present invention is to provide an optical pickup device having a structure capable of performing highly accurate servo control by eliminating crosstalk of a recording beam, which is unnecessary for servo control, to a light receiving element.

A sixth object of the present invention is to provide an information recording / reproducing apparatus having a structure capable of controlling the recording / verifying process at high speed in a stable manner by achieving the first to fifth objects. is there.

[0013]

The invention according to claim 1 is
A light source that emits a plurality of light fluxes, a polarization plane rotating means that rotates a part or all of the polarization planes of the light source by a predetermined angle, and an objective lens for converging the light emitted from the light source onto an information recording medium. In the optical pickup device equipped with, the polarization plane rotation angle θ of the beam incident on the objective lens is
1, θ2 ... θn (n> 2) corresponding to the spot intensities P1, P2, ... Pn focused on the information recording medium
However, P1>P2>...> Pn ... (1) or P1 <P2 <... <Pn ... (2) is satisfied.

According to a second aspect of the invention, in the optical pickup device, one of the light sources has a polarization plane rotating means of 1/2.
A two-channel array light source having a wave plate is provided, and the spot intensity emitted from both channels and condensed on the information recording medium corresponds to any of recording power, reproducing power and verifying power. There is.

According to a third aspect of the present invention, there is provided an angle reducing means for reducing the difference in the incident angles of the objective lenses of the light beams emitted from the light sources.

According to a fourth aspect of the present invention, a part of the light emitted from the light source and directed to the optical storage medium is separated from the first light path separating means for separating the respective light fluxes corresponding to respective polarization plane rotation angles. A light receiving element for detecting the light amount of each light flux is provided, and the output control of each corresponding light source is performed based on each light amount detected separately.

According to a fifth aspect of the present invention, the second optical path separating means for separating the light reflected from the information recording medium into light beams corresponding to the rotation angle of the polarization plane, and the light amount of each of the separated light beams are provided. A light receiving element for detection is provided, and reading of an information signal of an information recording medium, detection of a servo control signal, or detection of an address signal is performed on the basis of each reflected light detected separately.

According to a sixth aspect of the present invention, the angle reducing means, the first optical path separating means, or the second optical path separating means is a polarization hologram.

According to a seventh aspect of the present invention, the angle reducing means, the first optical path separating means, or the second optical path separating means is a Wollaston prism.

The invention according to claim 8 is characterized in that the angle reducing means, the first optical path separating means or the second optical path separating means is a beam splitter provided with a polarization selective thin film.

The invention according to claim 9 is characterized in that the angle reducing means is a wedge-shaped prism for correcting the beam shape of at least one of the polarization plane rotation angles into a substantially circular shape.

According to a tenth aspect of the invention, the beam shape having the rotation angle of the polarization plane is 2 for recording and reproducing and verifying.
Among the beams, the reproduction / verify beam is characterized in that the beam shaping magnification is higher than that of the recording beam.

In the eleventh aspect of the present invention, the beam shape having the rotation angle of the polarization plane is 2 for recording and reproducing and verifying.
It is characterized in that the reproduction and verify beams among the respective beams pass through an optical path in a polarization direction having a low total transmittance from the light source to the objective lens.

According to a twelfth aspect of the present invention, the recording and reproducing / verifying two kinds of polarization rotation angles which are substantially orthogonal to each other are provided, and the reproducing / verifying beam is used for tracking or focusing, and only the beam is selectively selected. It is characterized in that the polarization plane selecting means for transmitting the light to the optical recording medium is arranged in front of the light receiving element for detecting the reflected light from the information recording medium.

The thirteenth aspect of the invention is characterized in that the polarization plane selecting means is a polarization filter.

The invention according to claim 14 is the invention according to any one of claims 1 to 1.
The optical pickup device described in any one of 3 is used for an information recording / reproducing device.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an optical system in an optical pickup device according to the present invention. In FIG. 1, the optical pickup device of the present invention includes a light source unit 1 having two light emitting points, a collimator lens 2, a half mirror 5, a deflecting mirror 6, an objective lens 7, and light receiving elements 10 and 11. At the same time, the angle reducing means 4 for reducing the deviation of the incident angle to the objective lens 7, the first optical path separating means 12 for separating and detecting the monitor signal for light source control according to each emission beam, and each signal light from the board surface are detected. The second optical path separating means 9 for

A semiconductor laser chip is mounted on the light source unit 1, and two semiconductor laser chips are mounted on this semiconductor laser chip.
Two laser emission points LD1 and LD2 are provided. Two light beams are emitted from the two laser emission points LD1 and LD2, respectively.

A half-wave plate 2 is bonded to half of the semiconductor laser chip. The polarization planes of one light beam are rotated 90 degrees by the half-wave plate 2, and the polarization planes of the two light beams are orthogonal to each other.

The two beams emitted from the light source unit 1 are converted into substantially parallel light by the collimator lens 3. In particular,
The tilt angles of the beams that have passed through the collimator lens 3 are different from each other, and the angle difference is reduced by the angle difference reducing means 4 described later than immediately after the collimator lens is emitted.
Both beams, the difference in tilt angle of which has been reduced by the angle difference reducing means 4, pass through the half mirror 5, the optical path is bent by 90 degrees by the deflection mirror 6, and are condensed by the objective lens 7.
As shown in FIG. 2, the information recording track of the optical disc, which is the information recording medium 8, is irradiated.

The reflected light from the information recording medium 8 reverses the optical path at the time of irradiation, reaches the half mirror 5 again through the objective lens 7 and the deflection mirror 6. Unlike the case of irradiation, this reflected light is reflected by the half mirror 5 and reaches the second optical path separating means 9. The second optical path separating means 9 separates both beams by transmitting, reflecting, or diffracting the incident reflected light according to the polarization rotation angle, and guides it to the light receiving elements 10 and 11.

The light receiving elements 10 and 11 are appropriately divided according to the method of generating the servo signal. The reflected light from the information recording medium detected by the light receiving elements 10 and 11 is output to a control circuit (not shown) as a tracking signal, a focus signal and a reproduction signal.

In FIG. 1, a part of the light emitted from the light source unit 1 toward the information recording medium 8 is reflected without passing through the half mirror 5, and as a result, is not used for irradiation of the information storage medium. The reflected light of this extra light is detected by the monitor light receiving elements 13 and 14, and a detection signal proportional to the power of the light beam is output. In particular, the monitor light receiving element 1
In front of 3, 14 is arranged a first optical path separating means 12 for separating the two beams by transmitting, reflecting or diffracting them according to the polarization rotation angle.

In FIG. 2, both beams from LD1 and LD2 are used as a recording beam and a reproducing / verifying beam, respectively. In the information recording / reproducing system using the optical pickup device, first, the spot of the light flux for performing the recording by accessing is positioned at a desired address,
After that, recording is performed, and then confirmation reproduction is performed in order to confirm (verify) whether the recording is completed. In the multi-beam optical pickup device as in the present invention, the recording spot (S1) formed on the information recording medium by the beam emitted from the LD1 precedes and the LD2 on the same track of several μm to several tens μm behind the recording spot (S1). The verifying beam (S2) formed by the outgoing beam from is followed. On the other hand, during reproduction, only LD2 is caused to emit light (S3).

In the configuration shown in FIG. 1, the angle difference reducing means 4 for reducing the angle difference between the beams from the semiconductor lasers LD1 and LD2 in the light source unit 1, that is, the angle difference between the beams incident on the collimator lens 3. Are arranged between the collimator lens 3 and the objective lens 7.
Generally, when the incident beam on the objective lens 7 is inclined with respect to the optical axis of the objective lens 7, the wavefront deterioration is accompanied and the spot performance on the board cannot be secured. Especially the objective lens 7 has a high N
The deterioration becomes larger as it becomes A.

FIG. 3 shows the calculation results of the incident angle of the objective lens and the wavefront aberration. As is clear from the figure, the incident angle and the wavefront aberration have a proportional relationship. For this reason,
In the configuration shown in FIG. 1, by disposing the angle difference reducing means 4, the beams from the semiconductor lasers LD1 and LD2 are incident on the objective lens 7 without having to narrow the intervals between the semiconductor lasers. It prevents the oblique incidence. As a result, the spot intensity (P1, P1) focused on the information recording medium 8 is reduced by reducing the angle difference corresponding to the rotation angle of the polarization plane to the objective lens 7, for example, θ1, θ2 ... θn (n> 2). P2 ... Pn) is P1>P2>
..Pn or P1 <P2 <.. Pn As described above, although it is expected that the oblique incidence can be suppressed by reducing the distance between the semiconductor lasers, this method has a problem in securing accuracy in manufacturing and further causes thermal interference between the semiconductor lasers. Problems are likely to occur and it is impossible to narrow them to the extreme. Therefore, the distance between the semiconductor lasers is often set to several tens of μm, and it is undeniable that the tilt angle of the beam increases due to this.

In the configuration shown in FIG. 1, one light beam emitted from the light source unit 1 is rotated by 90 ° by the half-wave plate 2 so that the polarization planes of the two light beams are orthogonal to each other. Therefore, an element having polarization selectivity can be applied as the angle difference reducing means 4. As the angle reducing means, which will be described in detail later, the polarization hologram 1 used as the polarization selecting means.
5, the Wollaston prism 16, the polarization beam splitter 24, and the like. Further, the beam shaping prism 17 used for converting the elliptical beam into a substantially circular shape is also applicable. The components used in the angle difference reducing means 4 will be described below. First, the case where the polarization hologram 15 is used in FIG. 4 will be described. The polarization hologram 15 is a known optical element having a different diffractive action depending on the polarization state of the transmitted light beam. In this embodiment, since the polarization planes of the two light beams emitted from the light source unit 1 are orthogonal to each other, the LD emitted from the collimator lens 3 is emitted.
1, it is possible to reduce the angular difference between the beams from the LD 2. The polarization hologram 15 is made of LiNbO3 or Ca.
Some are made of a birefringent crystal material such as CO3. It is also possible to form an anisotropic film made of a low-cost organic substance or inorganic substance as a material on a glass substrate. The latter is also characterized in that the wavefront deterioration due to the incident angle is low.

Next, the case where the Wollaston prism 16 is used in FIG. 5 will be described. The Wollaston prism 16 uses birefringence and has two orthogonal polarization planes.
Although it is a prism that is generally used for splitting into two rays, it can also be used as a means to reduce the angle difference between two beams having different polarization planes. The Wollaston prism 16 is formed by joining uniaxial crystals such as calcite and quartz. In a uniaxial crystal, the refractive index differs depending on the vibration direction of light (polarized light) and the direction of the optical axis of the crystal. Utilizing this, two triangular prisms having different optical axis directions are bonded together. Since the directions of the optical axes are different before and after the cemented surface, the way of refraction depends on the polarized light. That is, the refraction angle differs between an extraordinary ray that oscillates in a plane including the ray and the optical axis and an ordinary ray that oscillates in a direction orthogonal to the extraordinary ray. As a result, the light rays are separated into two or combined into two and emitted.

Further, a case where the wedge prism 17 is used in FIG. 6 will be described. Wedge prism 17
Is generally used as a beam shaping prism in an optical pickup device. That is, the semiconductor laser emits a laser beam whose divergence angle differs depending on the axis parallel to the active layer and the axis perpendicular to the active layer. Therefore, the intensity distribution in the cross section perpendicular to the optical axis of the light flux made parallel by the collimator lens 3 has an elliptical shape, and the ratio of the laser beams emitted from many semiconductor lasers is 1: 2 or more. A beam shaping prism is known as a means for shaping the elliptical intensity distribution into a substantially circular shape. An elliptical beam having a short horizontal direction is made incident on a surface of the prism which is inclined in the horizontal direction, and is refracted by the first surface to widen the horizontal direction. The refraction on the first surface does not change the width of the beam in the direction perpendicular to the paper surface, so that the intensity distribution of the elliptical beam is shaped and a substantially circular intensity distribution can be obtained. By irradiating the optical storage medium with the laser beam shaped into a substantially circular shape through the objective lens 7, the spot diameter can be reduced and a more circular spot can be obtained. Therefore, an optical pickup device suitable for reproduction can be realized. In particular, in this embodiment, as described above, the wedge-shaped prism 17, which is generally used as a beam shaping prism, allows two beams having different angles to pass therethrough,
It is possible to reduce the beam shaping and its angular difference.

In FIG. 1, a part of the light emitted from the light source unit 1 toward the information recording medium is reflected without passing through the half mirror 5, and as a result, is not used for irradiation of the information storage medium. In the present invention, the reflected light of this extra light is
Detected by the monitor light receiving elements 13 and 14, a detection signal proportional to the power of the light beam is output. In particular, in front of the monitor light-receiving elements 13 and 14, there is arranged a first optical path separating means 12 for separating the two beams by transmitting, reflecting or diffracting them according to the polarization rotation angle.

Although not shown, the detection signals from the monitor light receiving elements 13 and 14 are compared with a predetermined reference value in the output control circuits of the semiconductor lasers LD1 and LD2, and a drive signal corresponding to the difference between the detection signal and the reference value. Is generated and supplied to each channel of the light source unit 1. As a result, the power of the light beam of each channel emitted from the light source unit 1 is controlled, and the monitor light receiving elements 13 and 14 are controlled.
Since the feedback is performed so that the difference between the detection signal of 1) and the reference value approaches zero, control is performed so that the power of the light beam is always kept constant.

Examples of the first optical path separating means 12 include a polarization hologram 20, a Wollaston prism 21 and a polarization beam splitter 19, which will be described in detail below. The constituent members of the first optical path separating unit 12 will be described below.

First, the case where the polarization hologram 20 is used in FIG. 8 will be described. The polarization hologram 20 is a known optical element having a different diffractive action depending on the polarization state of the transmitted light beam. In this embodiment, since the polarization planes of the two light beams emitted from the light source unit 1 are orthogonal to each other, a part of the light reflected by the half mirror 5 and not directed to the surface of the information recording medium can be polarized and separated. It will be possible. Each polarized beam is incident on the corresponding light receiving element 22. The light receiving element 22 is obtained by integrating the light receiving elements 10 and 11 in one package, and is excellent in terms of assembling and miniaturization.

Next, the case where the Wollaston prism 21 is used in FIG. 9 will be described. The Wollaston prism 21 is a prism that is generally used to utilize birefringence and separate it into two rays having orthogonal polarization planes.

Further, the case where the polarization beam splitter 19 is used in FIG. 7 will be described. The polarization selective film has different reflectance depending on the wavelength and polarization state of the laser beam. About 100% for one laser beam
Of the laser beam (that is, a reflectance of about 0%), and the other laser beam is reflected at a reflectance of about 100%. As a result, the light receiving element capable of receiving one beam from the polarization beam splitter 19 (in FIG. 1,
Since the elements denoted by reference numerals 10, 11, 13, and 14 correspond to the elements, the beams are separated toward the respective elements shown in FIG. 7 collectively.

In the configuration shown in FIG. 1, one light beam emitted from the light source unit has its polarization plane rotated 90 degrees by the half-wave plate 2 so that the polarization planes of the two light beams are orthogonal to each other. be able to. The reflected light of these light beams from the information recording medium is converted into the second optical path separating means 9
As a result, it is possible to completely separate the two light beams according to the difference in the plane of polarization. Therefore, as shown in FIG. 10, even if the light receiving elements 50 to 200 μm are widely separated, the track signal and the focus signal , Playback signal can be detected.

The second optical path separating means 9 may be the same polarization selecting means as the first optical path separating means 12.

In the structure shown in FIG. 1, both beams from the semiconductor lasers LD1 and LD2 are used as a recording beam and a reproducing / verifying beam, respectively. The recording beam and the reproducing / verifying beam have an intensity ratio of about 1: 5 to 1:15 on the board surface. Further, the higher the recording power, the easier it is to increase the speed. Therefore, in the present embodiment, when the maximum emission powers of the semiconductor lasers LD1 and LD2 are the same, reproduction and reproduction are performed so as to pass through the optical path in the polarization direction where the light utilization efficiency from the light source to the board surface of the information recording medium becomes low. The light amount distribution is set so that the verify beam passes through and the recording beam passes through the optical path in the polarization direction where the light utilization efficiency is high.

The servo control, that is, the position control of the actuator, in the optical pickup device having the structure shown in FIG. 1 is as follows. Between the optical pickup and the information recording medium 8, there is always a surface deviation of about 0.05 to 0.3 mm. On the other hand, the depth of focus of the objective lens 7 is ± 1 μm or less. That is, since the surface deviation of the information recording medium 8 is much larger than the focal depth, the objective lens 7 is moved up and down to perform focus control so that the distance between the objective lens 7 and the information recording medium falls within the focal depth of the objective lens 7. There is. A knife edge method, an astigmatism method, a double beam size method, or the like is used as a detection method for obtaining the focus error.

Further, the information recording medium 8 also changes in the direction orthogonal to the plane wobbling direction. That is, due to the eccentricity of the track of the information recording medium 8 and the axial deviation of the rotation axis of the turntable, the eccentricity of about 50 to 200 μm is generated with respect to the position of the laser beam emitted from the objective lens 7. In order to accurately read and write on a track, the laser beam must accurately track the track. Since this tracking accuracy generally has to be within ± 0.1, tracking control is performed. Known methods for detecting the track error include a push-pull method, a differential push-pull method (DPP method), and a phase difference method (DPD method). Regarding the generation of these signals, there are a method of generating the reflected light of the preceding recording beam, a method of generating either one of the reflected light of the reproducing / verifying beam, or a method of generating the reflected light of both beams. is there.
Particularly, when the servo control is performed only by the reflected light of the reproducing / verifying beam, only one light receiving element is required.

Next, another example according to the embodiment of the present invention will be described. FIG. 11 is a diagram showing a configuration of an optical pickup device according to another example of the embodiment of the present invention. The configuration shown in FIG. 11 is different from the configuration shown in FIG. 1, and the second optical path separation shown in FIG. Instead of the means 9, the optical path selection means 23 is used. Further, in the configuration shown in FIG. 11, as the angle difference reducing means 4, a reflection type beam shaping prism 24 having a polarization selection surface as shown in FIG. 12 (a polarizing film is shown by C in FIG. 12) is used. ing.

As shown in FIG. 12, the semiconductor laser LD1
After passing through the collimator lens 3, the recording beam emitted from the laser beam enters the beam shaping prism 24 at a predetermined angle, is reflected by the polarization plane, and is emitted from the same plane as the incident plane toward the objective lens. The polarization selection surface (C1) is formed with a polarization selection film similar to the polarization beam splitter 19 that transmits / reflects according to the polarization direction of the incident light.

The reproducing / verifying beam emitted from the semiconductor laser LD2, after passing through the collimating lens 3, is incident on the beam shaping prism 24 at a predetermined angle, is transmitted through the polarization plane, and is incident on the rear surface of the beam shaping prism incidence plane. When reflected and transmitted through the plane of polarization again, it is emitted toward the objective lens 7 from the same plane as the plane of incidence.

Each beam is condensed by the objective lens 7 and is irradiated onto the information recording track of the optical disc which is the information recording medium 8. The reflected light travels in the reverse optical path at the time of irradiation, and the objective lens 7 and It reaches the half mirror 5 through the deflection mirror 6. The reflected light is reflected by the half mirror 5 and reaches the optical path selecting means 23, unlike the case of irradiation.

As the optical path selecting means 23, a polarizing filter which selectively transmits the incident reflected light according to the polarization rotation angle thereof can be mentioned. The light receiving element may be only a light receiving element that detects only the reproducing / verifying beam. The light receiving element is appropriately divided according to the method of generating the servo signal. The reflected light from the information recording medium detected by the light receiving element is output to a position control circuit (not shown) of the actuator as a tracking signal, a focus signal and a reproduction signal.

In the structure shown in FIG. 11, the beam is shaped by the following procedure. Figure 11
In the configuration shown in (1), the read / verify beam has a higher beam shaping magnification than the recording beam. Further, the beam shaping direction is set in the radial direction of the information recording medium. As a result, the recording beam secures spot performance in the rotation direction of the information recording medium (called the jitter direction), and the reproducing / verifying beam secures spot performance in both directions. As a result, stable servo control can be performed by the reproduction / verify beam. The spots on the information recording medium at this time are shown in FIG. In FIG. 13, both spots (S4, S5, S6) are narrowed down in the jitter direction, while in the radial direction, a verify / playback beam (S) for reading an information signal and generating a focus signal is performed.
5, S6) only.

As the optical path selection means 23 used in the configuration shown in FIG. 11, a polarization filter can be mentioned. That is,
Light is a plane wave and has a plurality of electric field components (polarized light) that vibrate perpendicularly to the traveling direction. A polarizing filter is mentioned as a filter having a function of separating a specific polarized light (linearly polarized light) from this light, which is also called a polarizer. For this polarization filter, a birefringence type that uses the birefringence of a single crystal such as a Nicol prism, a two-color type that uses dichroism such as polaroid polymer or rod-shaped metal fine particles, and a difference in polarization angle are used. There are reflection type and interference filter type. By disposing such a polarization filter in the polarization direction that transmits only the reproduction / verify beam, it is possible to eliminate unnecessary recording beams as servo signals during recording.
During reproduction, stable detection of servo signals and information signals becomes possible.

Next, another example according to the embodiment of the present invention will be described. FIG. 14 shows an information recording / reproducing apparatus equipped with the optical pickup device having the configuration shown in FIG. 1 or 11, and the information recording / reproducing apparatus 30 shown in FIG. The carriage 32 is provided with the optical pickup device having the configuration described in 11, and the spindle motor 33 provided near the carriage 32. Note that FIG.
In FIG. 4, only the mechanical portion of the information recording / reproducing apparatus is shown, but it goes without saying that various signal processing circuits and input terminals are actually provided. Housing 3
On one side wall of No. 1 is provided a slot 31A into which the cartridge 34 containing the information recording medium 8 can be inserted into and removed from the spindle motor 33. The cartridge 34 has a built-in optical disk which is a rotatable information recording medium 8. A part of the optical disk is the cartridge 34.
It can be exposed to the outside through the window formed in the. The window portion is dust-proofed by a shutter 35 that is opened in association with the insertion of the cartridge into the housing 31. The cartridge 34 has an arrow A
The carriage 32 is inserted into the housing 31 along the direction indicated by, and the position of the carriage 32 is adjusted in the direction along arrow B so that the optical pickup device is positioned in the tracking direction. Further, in the carriage 32, the position of the objective lens 7 is adjusted in the focusing direction, and the light utilization efficiency of the beam, the spot diameter, the laser output and the signal modulation degree are optimized together with the tracking direction. In the above-mentioned example, regarding the polarization rotation angle, one polarization plane of two light beams emitted from the light emitting means of the multi-beam optical head is set to 9
The example of using the half-wave plate as the polarization plane rotating means for rotating by 0 degree has been described, but the present invention is not limited to this, and a part or all of the polarization planes of a plurality of light beams are rotated by a predetermined angle. It may be an optical member that can be used. Further, in that case, the polarization splitting means is not limited to the polarization beam splitter, and may be any optical member that splits light into a plurality of light fluxes according to the degree of polarization and emits the light fluxes in different optical paths.

[0059]

According to the inventions of claims 1 and 2,
A light source that emits a plurality of light fluxes, a polarization plane rotating means that rotates a part or all of the polarization planes of the light source by a predetermined angle, and an objective lens for converging the light emitted from the light source onto an information recording medium. In the optical pickup device equipped with, the polarization plane rotation angle θ of the beam incident on the objective lens is
1, θ2 ... θn (n> 2) corresponding to the spot intensities P1, P2, ... Pn focused on the information recording medium
However, since P1>P2>...> Pn ... (1) or P1 <P2 <... <Pn ... (2) is satisfied, the difference in the angle of incidence on the objective lens is reduced. It is possible to secure the wavefront performance by means of, stabilize the control of the light source output power by distributing the optical path to the monitor light receiving element, stabilize the servo control by distributing the optical path to the board surface reflected light receiving element, and improve the reproduction characteristics of the information recording signal. it can. In particular, it can have an effect on stable signal output to a control system in a recording / verifying / reproducing system.

According to the invention described in claims 3 and 6 to 9, the angle reducing means (polarization hologram, Wollaston prism, wedge prism, polarization) for reducing the difference in the incident angle of the objective lens of each light flux emitted from each light source. Since the beam splitter is provided, it is possible to secure the spot performance of the beam from each light source condensed by the objective lens.

According to the fourth and sixth to eighth aspects of the present invention, a part of the light emitted from each light source and directed to the optical storage medium is separated into the respective light fluxes corresponding to the respective polarization plane rotation angles. A means (a polarization hologram, a Wollaston prism, a polarization beam splitter, etc.) and a light receiving element for detecting the light amount of each separated light flux are provided, and the output control of each corresponding light source is performed based on each separated and detected light amount. As a result, it becomes possible to detect the emission power from each light source with high reliability and to perform stable feedback to each light source.

According to the fifth to eighth aspects of the invention, the second optical path separating means (polarization hologram, which separates the light reflected from the information recording medium into a plurality of light beams according to the rotation angle of the polarization plane and emits the light beams through different optical paths. (Wollaston prism, polarization beam splitter) is arranged in front of each light receiving element corresponding to the light source, and the reflected light from the information recording medium of the light emitted from each light source is separated and detected. It is possible to detect each beam with high reliability and generate a servo signal and an information signal.

According to the tenth aspect of the present invention, since the beam shaping magnification of the reproduction / verify beam is set higher than that of the recording beam, in the system performing tracking by the reproduction / verify beam, It is possible to secure the spot performance in both directions of the jitter direction.

According to the eleventh aspect of the invention, since the reproducing / verifying beam is configured to pass through the optical path in the polarization direction having a low total transmittance from the light source to the objective lens, high light utilization efficiency is required. The power of the recording beam can be secured.

According to the twelfth and thirteenth aspects of the present invention, tracking or focusing is performed by one of the reproducing and verifying beams, and the polarization plane selecting means for selectively transmitting only the beam is received. Since it is arranged in the preceding stage of the element, it is possible to eliminate crosstalk of the recording beam, which is unnecessary for servo control, to the light receiving element.

According to the fourteenth aspect of the present invention, it is possible to obtain an information recording / reproducing apparatus capable of stable signal control.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of an optical pickup device for explaining an embodiment of the present invention.

FIG. 2 is a diagram for explaining spot positions for recording / reproducing / verifying on the surface of an information recording medium.

FIG. 3 is a diagram showing a relationship between a beam incident angle on an objective lens and a wavefront aberration.

FIG. 4 is a diagram showing an example in which a polarization hologram is used as an angle difference reducing means.

FIG. 5 is a diagram showing an example in which a Wollaston prism is used as an angle difference reducing means.

FIG. 6 is a diagram showing a case where a beam shaping prism is used as an angle difference reducing means.

FIG. 7 is a diagram showing a case where a polarization beam splitter is used as a first optical path separating unit, in which (A) shows a configuration and (B) shows a configuration.
Indicate the light receiving surfaces, respectively.

8A and 8B are diagrams showing a case where a polarization hologram is used as a first optical path separating unit, in which FIG. 8A shows a configuration and FIG. 8B shows a light receiving surface.

FIG. 9 is a diagram showing a case where a Wollaston prism is used as the first optical path separating means, and FIG.
(B) shows the respective light receiving surfaces.

10 is a diagram showing an arrangement relationship of light receiving elements in the optical pickup device having the configuration shown in FIG.

FIG. 11 is a schematic diagram for explaining a configuration of an optical pickup device according to another example of the embodiment of the present invention.

12 is a diagram showing a case where a beam shaping prism is used as one of the polarization selection configurations in the optical pickup device shown in FIG.

13 is a diagram for explaining spot positions on the surface of an information recording medium in the optical pickup device having the configuration shown in FIG.

FIG. 14 is a diagram for explaining a main part configuration of an information recording / reproducing apparatus equipped with the optical pickup device having the configuration shown in FIG. 1 or FIG.

FIG. 15 is a schematic diagram showing a conventional example of an optical pickup device using a multi-beam.

16 is a schematic diagram for explaining an optical path of a reflected beam in the optical pickup device using the multi-beam shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Light source unit 2 Polarization plane rotating means 3 Collimating lens 4 Angle difference reducing means 5 Half mirror 6 Polarizing mirror 7 Objective lens 8 Information recording medium 9 Second optical path separating means 10 Recording beam detecting light receiving element 11 Reproducing / verifying beam detecting Light receiving element 12 First optical path separating means 13 and 14 Light source monitoring light receiving element 15 Polarization hologram 16 which is an example of angle difference reducing means Wollaston prism 17 which is another example of angle difference reducing means Another example of angle difference reducing means Beam shaping prism 19 Polarizing beam splitter 20 which is an example of first optical path separating means Polarization hologram 21 which is another example of first optical path separating means Wollaston prism 22 which is another example of first optical path separating means 22 Separated beam Light receiving element 23 Optical path selecting means 30 Information recording / reproducing device 31 Housing 32 Optical pickup device Mounting the carriage 33 cartridge that contains the spindle motor 34 concessions recording medium

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5D090 AA01 BB04 CC01 CC04 CC16                       CC18 EE01 EE11 EE18 FF31                       HH01 KK03 KK13 LL08                 5D119 AA43 BA01 BB03 DA01 DA05                       DA07 FA09 HA12 HA23 JA07                       JA30 JA63                 5D789 AA43 BA01 BB03 DA01 DA05                       DA07 FA09 HA12 HA23 JA07                       JA30 JA63

Claims (14)

[Claims] 1. A light source for emitting a plurality of light beams, a polarization plane rotating means for rotating a part or all of the polarization planes of the light source by a predetermined angle, and light emitted from the light source is condensed on an information recording medium. In an optical pickup device equipped with an objective lens for adjusting the polarization plane rotation angles θ1 and θ of the incident beam to the objective lens.
2 ... .theta.n (n> 2), the spot intensities P1, P2, ... Pn focused on the information recording medium are P1> P2 >>...> Pn ... (1) Alternatively, an optical pickup device characterized by satisfying P1 <P2 <... <Pn (2). 2. The optical pickup device is provided with a two-channel array light source in which one light source is provided with a ½ wavelength plate as a polarization plane rotating means, and is emitted from both channels and collected on an information recording medium. 2. The optical pickup device according to claim 1, wherein the intensity of the spot to be emitted corresponds to any of recording power, reproducing power and verifying power. 3. The optical pickup device according to claim 1, further comprising angle reducing means for reducing a difference in incident angle of the objective lens of each light beam emitted from each light source. 4. A first optical path separating means for separating a part of light emitted from the light source and directed to an optical storage medium into light beams corresponding to respective rotation angles of polarization planes, and a light amount of each of the separated light beams. It is equipped with a light receiving element that
4. The optical pickup device according to claim 1, wherein the output control of each corresponding light source is performed. 5. A second optical path separating means for separating the light reflected from the information recording medium into light fluxes corresponding to the rotation angle of the polarization plane, and a light receiving element for detecting the light quantity of each of the separated light fluxes. The information signal of the information recording medium is read, the servo control signal is detected, or the address signal is detected on the basis of the reflected light that is separately detected. The optical pickup device described in one. 6. The optical pickup device as claimed in claim 1, wherein the angle reducing means, the first optical path separating means, or the second optical path separating means is a polarization hologram. . 7. The light according to claim 3, wherein the angle reducing means, the first optical path separating means, or the second optical path separating means is a Wollaston prism. Pickup device. 8. The angle reducing means, the first optical path separating means, or the second optical path separating means is a beam splitter having a polarization-selective thin film. The optical pickup device described in one. 9. The angle reducing means is a wedge-shaped prism that corrects a beam shape of at least one of the polarization plane rotation angles into a substantially circular shape, and the angle reducing means is a wedge-shaped prism. Optical pickup device. 10. The beam shape having the polarization plane rotation angle is set to have a relationship of being substantially orthogonal in two types of recording and reproducing / verifying, and the reproducing / verifying beam of each beam has a beam shaping magnification as compared with a recording beam. 10. The optical pickup device according to claim 9, wherein the height is raised. 11. A beam shape having the polarization plane rotation angle is set to have a relationship of being substantially orthogonal in two kinds of recording and reproducing / verifying, and the reproducing / verifying beam of each beam is from the light source to the objective lens. The optical pickup device according to claim 1, wherein the optical pickup device passes through an optical path having a polarization direction with a low total transmittance. 12. Polarized light for selectively transmitting only the beam having two kinds of polarization rotation angles of the recording and reproducing / verifying which are substantially orthogonal to each other and having a structure for performing tracking or focusing by a reproducing / verifying beam. 13. The optical pickup device according to claim 1, wherein the surface selection means is arranged in front of the light receiving element for detecting the reflected light from the information recording medium. 13. The optical pickup device according to claim 12, wherein the polarization plane selection means is a polarization filter. 14. An information recording / reproducing apparatus comprising the optical pickup device according to any one of claims 1 to 13.