JP2002100069A - Optical pickup and optical disk drive - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a recording optical pickup and an optical disk drive as small as possible, which overcome the problems of layout design of an optical system including a monitor photodetector. The present invention relates to an optical pickup used in an optical disk drive for irradiating an optical disk (15, 16) with a light beam to record or reproduce a digital signal. An objective lens 14 for guiding the light beam onto the optical disk, and an optical component 22 interposed in the optical path of the light beam, for transmitting or reflecting the light beam and emitting the light beam into the optical path;
Monitor photodetector 1 for monitoring the intensity of the light beam
7, wherein the optical component 22 and the monitor photodetector 17 are arranged such that the light beam is guided from the optical component 22 to the monitor photodetector 17. Solve the problem with an optical pickup.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup used in an optical disk drive, and more particularly to an optical pickup for irradiating a recordable optical disk with a light beam and an optical disk drive.

[0002]

2. Description of the Related Art Although a DVD disk and a CD disk have the same diameter of 12 cm (centimeter), the difference in track pitch between tracks for recording digital signals and the amount of digital data per unit track length, that is, linear density. The amount of digital data that can be recorded differs due to the difference. Specifically, 4.7 to 8.54 G (giga) bytes for DVD discs and 600 to 700 M (mega) for CD discs
The recording capacity differs greatly from bytes.

[0003] The DVD disk that has appeared as a large-capacity recording medium in this way may replace the CD disk in the future and dominate the market. However, CD discs have already spread widely in the market along with the spread of playback devices, and DVD disc playback devices cannot ignore the property of CD discs. A playback function is required as an essential function.

In a DVD disk reproducing apparatus, a compatible reproducing / recording function is also required for an optical pickup, which is an essential component, and in recent years, a reproducing beam for DVD and a reproducing / recording function for CD have been recently developed.
An optical pickup equipped with a dedicated light source for emitting a recording beam has been developed.

FIG. 8 is used to explain the prior art of the present invention.

FIG. 8 is a diagram showing an optical system of an optical pickup according to the prior art.

FIG. 8A is a side view of the optical system of the optical pickup. FIG. 2B is a top view of the optical system of the optical pickup.

In FIG. 8, reference numeral 45 denotes an optical disk, which is a DVD disk manufactured based on the DVD (digital versatile disk) standard. Also, 46
Is also an optical disk, which is a CD disk manufactured according to the CD (Compact Disk) standard.

In the optical system of the optical pickup shown in FIG. 8, reference numeral 44 denotes an objective lens.

In FIG. 1, reference numeral 31 denotes a DVD optical unit for emitting a light beam having a wavelength of 650 nm (nanometer) for a DVD disk.

Here, the DVD optical unit 31
A light source 32 composed of a laser diode that emits light at a wavelength of 50 nm and emits a light beam, and the emitted light beam is D
After irradiating the signal recording surface of the VD disk 45, a photodetector 33 composed of a photodiode for receiving light reflected by the signal recording surface and a light beam from a light source 32 are transmitted, and the reflected light Is diffracted and the photodetector 33
And a diffraction grating 34 for guiding the light to the light.

In the figure, 35 is CD / CD
780 for playback / recording of R / CD-RW discs
An optical unit for a CD for emitting a light beam having a wavelength of nm (nanometer).

A CD-R disc and a CD-RW disc are irradiated with a light beam having a wavelength of 780 nm, thereby causing a physical change on a signal recording surface and causing a portion having a different reflectance on the recording surface. It is an optical disk on which digital signals can be recorded by causing it to occur.

Similarly to the optical unit 31, the CD optical unit 35 includes a light source 36 composed of a laser diode that emits a light beam at a wavelength of 780 nm and emits a light beam, and a light beam emitted from the light source 36 After being irradiated on the signal recording surface, a light detector 37 composed of a photodiode for receiving the reflected light reflected on the signal recording surface and a light beam from the light source 36 are transmitted, and the reflected light is diffracted. The diffraction grating 38 leading to the photodetector 37 is integrated.

The light beams emitted from the DVD optical unit 31 and the CD optical unit 35 are both beam splitters 40, which are optical components made of a transparent resin.
Incident on.

The beam splitter 40 has a polyhedral shape, and a light beam emitted from the DVD optical unit 31 having a wavelength of 650 nm and a light beam emitted from the CD optical unit 35 having a wavelength of 780 nm are different from each other. From the beam splitter 40. In particular, the light beam emitted from the CD optical unit 35 enters the beam splitter 40 via the coupling lens 39.

Inside the beam splitter 40, there is provided a wavelength-selective dichroic coating surface 41. This dichroic coating reflects a light beam having a wavelength of 650 nm and transmits a light beam having a wavelength of 780 nm. Lead in a common direction.

A light beam having a wavelength of 650 nm and a light beam having a wavelength of 7
After passing through the dichroic surface 41, the 80 nm light beam exits the beam splitter 40 and enters the collimator lens 42. The collimating lens 42 converts a light beam having a wavelength of 650 nm and a light beam having a wavelength of 780 nm into parallel light beams and emits them.

The light beams of each wavelength emitted from the collimator lens 42 are guided to a dichroic filter 43.
The dichroic filter 43 is provided with a dichroic film for shaping the cross-sectional shape of the light beam incident on the objective lens 44 into a substantially circular shape having a predetermined numerical aperture.

Specifically, the beam spot shape of the light beam of each wavelength is such that the beam spot of the light beam having a wavelength of 650 nm is substantially circular with a numerical aperture of 0.6, and the beam spot of the light beam having a wavelength of 780 nm is a numerical aperture. It becomes a substantially circular shape of 0.5.

The light beams of each wavelength having passed through the dichroic filter 43 are made incident on an objective lens 44, guided to a DVD disk 45 and a CD disk 46, and focused on a signal recording surface of each disk.

The light beam having a wavelength of 650 nm reflected on the signal recording surface 45 of the DVD disk is reflected by the dichroic surface 41, guided to the optical unit 31, and incident on the diffraction grating 34 as return light. I do.

At this time, a wavelength of 6
First-order diffracted light is generated based on a 50 nm light beam,
The next-order diffracted light enters the photodetector 33 as signal light representing a digital signal on the signal recording surface of the optical disc 45.

An optical disk drive (not shown) reproduces a digital signal recorded on the DVD disk 45 based on the signal light.

On the other hand, the light beam having a wavelength of 780 nm reflected on the signal recording surface 46 of the CD disk is transmitted through the dichroic surface 41 and is transmitted to the optical unit 35.
And is incident on the diffraction grating 38 as return light.

At this time, a wavelength of 7
First-order diffracted light based on a light beam of 80 nm is generated.
The next-order diffracted light enters the photodetector 37 as signal light representing a digital signal on the signal recording surface of the optical disk 46.

An optical disk drive (not shown) reproduces a digital signal recorded on the CD disk 46 based on the signal light.

In the present optical system, when irradiating the CD-R disk and the CD-RW disk with a light beam of 780 nm, a monitor light detection for monitoring the intensity of the light beam emitted from the light source 36 is performed. A vessel 47 is provided.

Particularly, in the present embodiment, the monitor photodetector 47 is disposed in front of the light source 36 and receives and monitors a light beam emitted from the light source 36, so that it is called a front monitor type.

The monitor light detector 47 is a recordable CD.
APC (automatic light control) circuit (not shown) which is provided to strictly control the intensity of the light beam irradiated to the -R or CD-RW disc and generates a monitor signal by photoelectrically converting the monitored light amount. , The intensity of the light beam emitted from the light source 36 is feedback-controlled.

The monitor light detector 47 has a light receiving surface 4
The monitor signal is generated by irradiating the light receiving surface 48 with a light beam emitted from the light source 36 and receiving the light beam.

In recent years, with the miniaturization of the optical disk drive using the optical pickup as a key device, miniaturization of the optical pickup has been promoted. In order to reduce the size of an optical pickup, it is essential to reduce the area occupied by an optical system mounted on the optical pickup. In particular, in an optical pickup for recording, the layout of the optical system including the monitor photodetector and other optical components Design was a challenge.

[0033]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an optical pickup according to the present invention is used for an optical disk drive for irradiating an optical disk with a light beam and recording or reproducing a digital signal. A light source that emits a light beam, an objective lens that guides the light beam onto a signal recording surface of the optical disc, and intervenes in an optical path of the light beam to transmit or reflect the light beam. An optical component to be emitted into the optical path;
A monitor light detector that monitors the intensity of the light beam, wherein the optical component and the monitor light detector are arranged such that the light beam is guided from the optical component to the monitor light detector. It is characterized by having.

According to another aspect of the present invention, there is provided an optical pickup for irradiating an optical disk with a light beam.
An optical pickup used in an optical disk drive for recording or reproducing a digital signal, comprising: a first light beam and a second light source for emitting a first light beam and a second light beam having mutually different wavelengths; An objective lens for guiding the first light beam and the second light beam onto the signal recording surface of the optical disc, and an optical component on which the first light beam and the second light beam are incident; A transmission surface that transmits the light beam or a reflection surface that reflects the light beam,
An optical component that emits the first light beam and the second light beam together and guides the light beam to the objective lens, and monitor light detection that monitors the intensity of at least one of the first light beam and the second light beam. The optical component and the monitor photodetector, wherein the light beam monitors the intensity through a transmission surface or a reflection surface of the optical component, and the light beam is used as the monitor photodetector. It is characterized by being arranged so as to be guided to.

According to another aspect of the present invention, there is provided an optical disk drive for irradiating an optical disk with a light beam to record or reproduce a digital signal. First and second light sources for emitting different first and second light beams, and an object for guiding the first and second light beams onto a signal recording surface of the optical disk Lens and
An optical component on which the first light beam and the second light beam are incident, the optical component including a transmission surface that transmits the light beam or a reflection surface that reflects the light beam, and the first light beam and the second light beam; An optical component for emitting a light beam together and guiding the light beam to the objective lens, the first light beam or the second
A monitor light detector for monitoring the intensity of at least one of the light beams, wherein the optical component and the monitor light detector are arranged such that the light beam is transmitted or reflected by the optical component. An optical pickup arranged so that the light beam for monitoring the intensity is guided to the monitor photodetector, a turntable for mounting and rotating the disk, and the light A guide means for guiding a pickup in a radial direction of the optical disc is provided.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is used to explain a first embodiment of the present invention.

FIG. 1 is a diagram showing an optical system according to a first embodiment of the present invention.

FIG. 1A is a side view of the optical system of the optical pickup. FIG. 2B is a top view of the optical system of the optical pickup.

In FIG. 1, reference numeral 15 denotes an optical disk, which is a DVD disk manufactured based on the DVD (digital versatile disk) standard. Also, 16
Is also an optical disk, which is a CD disk manufactured according to the CD (Compact Disk) standard.

In the optical system of the optical pickup shown in FIG. 1, reference numeral 14 denotes an objective lens.

In FIG. 1, reference numeral 1 denotes a DVD optical unit for emitting a light beam having a wavelength of 650 nm (nanometer) for a DVD disk.

Here, the optical unit for DVD 1 is 65
A light source 2 composed of a laser diode that emits a light beam at a wavelength of 0 nm and emits a light beam;
After irradiating the signal recording surface of the disk 15, a photodetector 3 composed of a photodiode for receiving light reflected by the signal recording surface and a light beam from the light source 2 are transmitted, and the reflected light is transmitted. It is integrated with a diffraction grating 4 that diffracts light and leads it to a photodetector 3.

In the figure, 5 is CD / CD-
780n for playback / recording of R / CD-RW disc
It is a CD optical unit for emitting a light beam having a wavelength of m (nanometer).

The CD-R disc and the CD-RW disc are irradiated with a light beam having a wavelength of 780 nm, thereby causing a physical change on a signal recording surface to form portions having different reflectivities. This is an optical disc on which digital signals can be recorded.

Similarly to the optical unit 1, the CD optical unit 5 includes a light source 6 composed of a laser diode that emits light at a wavelength of 780 nm and emits a light beam, and the emitted light beam is applied to a signal recording surface of a CD disk 16. After irradiation, a photodetector 7 composed of a photodiode for receiving the reflected light reflected on the signal recording surface, a light beam from the light source 6 is transmitted, and the reflected light is diffracted to form a photodetector 7. And a diffraction grating 8 for guiding the light to the light.

The light beams emitted from the optical unit for DVD 1 and the optical unit for CD 5 both enter a beam splitter 10 which is an optical component formed of a transparent resin.

The beam splitter 10 has a polyhedral shape and has a wavelength of 6 out of the optical unit 1 for DVD.
The 50 nm light beam and the 780 nm light beam emitted from the CD optical unit 5 enter the beam splitter 10 from different surfaces. Above all, CD
The light beam emitted from the optical unit 5 is coupled to the coupling lens 9.
And enters the beam splitter 10.

A wavelength-selective dichroic coating surface 11 is provided inside the beam splitter 10, and this dichroic coating reflects a light beam having a wavelength of 650 nm and transmits a light beam having a wavelength of 780 nm. Lead them in a common direction.

A light beam having a wavelength of 650 nm and a light beam having a wavelength of 7
After passing through the dichroic surface 11, the 80 nm light beam passes through one surface 22 of the beam splitter 10, exits, and enters the collimator lens 12. The collimating lens 12 converts a light beam having a wavelength of 650 nm and a light beam having a wavelength of 780 nm into parallel light beams and emits them.

The light beams of each wavelength emitted from the collimator lens 12 are guided to a dichroic filter 13.
The dichroic filter 13 is a dichroic filter 13 provided with a dichroic coating for shaping the cross-sectional shape of the light beam incident on the objective lens 14 into a substantially circular shape having a predetermined numerical aperture.

The shape of the dichroic film applied to the dichroic filter 13 is shaped according to the shape of the beam spot to be irradiated on the signal recording surface of the optical disc according to the beam of each wavelength.

Specifically, the beam spot shape of the light beam of each wavelength is such that the beam spot of the light beam having the wavelength of 650 nm is substantially circular with a numerical aperture of 0.6, and the beam spot of the light beam having the wavelength of 780 nm is the numerical aperture. It becomes a substantially circular shape of 0.5.

The light beams of each wavelength having passed through the dichroic filter 13 are made incident on the objective lens 14, guided to the DVD disk 15 and the CD disk 16, and collected on the signal recording surface of each disk.

Then, the light beam having a wavelength of 650 nm reflected on the signal recording surface of the DVD disk 15 is reflected by the dichroic surface 11, guided to the optical unit 1, and incident on the diffraction grating 4 as return light. I do.

At this time, the wavelength from the diffraction grating 4 is 65
First-order diffracted light based on the light beam of 0 nm is generated, and the first-order diffracted light enters the photodetector 3 as signal light representing a digital signal on the signal recording surface of the optical disk 5.

An optical disk drive (not shown) reproduces or records a digital signal recorded on the DVD disk 15 based on the signal light.

On the other hand, the light beam having a wavelength of 780 nm reflected on the 16 signal recording surfaces of the CD disk is transmitted through the dichroic surface 11, guided to the optical unit 5, and enters the diffraction grating 8 as return light. I do.

At this time, the wavelength from the diffraction grating 8 is 78
First-order diffracted light based on the 0-nm light beam is generated, and the first-order diffracted light enters the photodetector 7 as signal light representing a digital signal on the signal recording surface of the optical disc 16.

An optical disk drive (not shown) reproduces or records a digital signal recorded on the CD disk 16 based on the signal light.

As described above, the beam splitter 10
650nm wavelength light beam for D and 780n for CD
The light beam of m wavelengths is guided to the objective lens 14 and the reflected light from the signal recording surface of the optical disk is converted to a DVD.
Optical unit 15 and the optical unit 16 for CD.

In the present optical system, when irradiating the CD-R disk and the CD-RW disk with a light beam of 780 nm, a monitor light detection for monitoring the intensity of the light beam emitted from the light source 6 is performed. A vessel 17 is provided.

In particular, in this embodiment, the monitor photodetector 17 is disposed in front of the light source 6 and receives and monitors a light beam emitted from the light source 6, so that it is called a front monitor method.

The monitor photodetector 17 has a recordable CD.
APC (automatic light control) circuit (not shown) which is provided to strictly control the intensity of the light beam irradiated to the -R or CD-RW disc and generates a monitor signal by photoelectrically converting the monitored light amount. , The intensity of the light beam emitted from the light source 6 is feedback-controlled.

The monitor light detector 17 has a light receiving surface 1
The monitor signal is generated by irradiating the light receiving surface 18 with a light beam emitted from the light source 6 and receiving the light beam.

At this time, the light receiving surface 18 emitted from the light source 6
The light beam irradiated on the beam splitter 10 travels along the optical path 19 and enters the beam splitter 10.
The light is reflected by the surface 20 through which the light beam having the wavelength of 50 nm transmits as a reflection surface, and then received by the monitor photodetector 17.

In the above embodiment, the monitor photodetector 17
The light beam is reflected and guided to the monitor light detector 17 by providing one of the surfaces of the beam splitter 10 with an optical deflection characteristic or a diffraction characteristic and deflecting, refracting or diffracting the light on this surface. May lead.

However, in any case, the optical component for guiding the light beam and the monitor photodetector must be arranged so as to receive the light beam guided from the optical component.

In particular, in the present embodiment, the light emitted forward from the light source 6 can be guided to the monitor photodetector arranged on the side of the optical path by the optical components arranged in the optical path. It is suitable for the optical pickup of the system.

By the way, in the front monitor type optical pickup as in the first embodiment, the variation in the spread angle of the substantially conical light beam emitted from the light source 6 constituting the optical system, and the difference between the light source 6 and the light source 6 are different. , A beam splitter 10,
Due to the variation in the mounting position of the monitor photodetector 17 in the base, the light amount of the light beam that enters the light receiving surface 18 of the monitor detector 17 from the light source 6 via the beam splitter 10 occurs.

The polygonal beam splitter 10
The light amount of the light beam incident on the light receiving surface 18 of the monitor detector 17 varies due to variations in transmittance and reflectance of each surface.

In the present embodiment, the beam splitter 10 shown in FIG.
A surface 21 on which a light beam having a wavelength of 780 nm is incident;
A surface 20 on which a light beam having a wavelength of nm is incident, and a surface 22 on which light beams having a wavelength of 780 nm and 650 nm incident on the beam splitter 10 are both emitted.

Of these surfaces, a part of the light beam of the 780 nm wavelength light beam on the surface 20 is reflected and guided to the monitor photodetector 17.

Here, the reflectivity of the surface 20 for reflecting the light beam of the 780 nm wavelength in the direction of incidence on the monitor detector 17 is such that the light beam of the 780 nm wavelength enters the beam splitter 10 after the light beam enters the beam splitter 10. Is larger than the reflectivity for a light beam having a wavelength of 780 nm.

As described above, the wavelength 7 for the CD disk 16 is used.
By increasing the reflectance of the surface 20 for the 80 nm light beam with respect to the reflectance of the surface 22 for this light beam, the light amount of the light beam of the light source 6 incident on the light receiving surface 18 of the monitor detector 17 can be reduced. Stabilize and CD
Unnecessary stray light component incident on the photodetector 7 in the optical unit 5 can be reduced.

A surface 23 of one of the surfaces of the beam splitter 10 which faces the light receiving surface 18 of the monitor photodetector 17 is mirror-finished, and the wavelength of light reflected irregularly on the surface of the monitor photodetector 17 is obtained. The light of 780 nm is reflected so that it can enter the light receiving surface 18 again.

Next, FIG. 2 will be used to describe a second embodiment obtained by further improving the first embodiment.

FIG. 2 is a diagram showing an optical system of an optical pickup according to a second embodiment of the present invention.

In the figure, an optical unit 1 having a diffraction grating 8, a light source 6, and a photodetector 7, an optical unit 5, a coupling lens 9, a beam splitter 10, a collimating lens 12, a dichroic filter 13, an objective lens 14,
The optical path 19 of the light beam emitted from the light source 2 in the optical unit 1 and guided by the beam splitter 10 constitutes the optical system of the optical pickup of the first embodiment. It is the same as the element part which performs.

The DV to be reproduced or recorded is
The D disk 15 or the CD disk 16 is the same as that of the first embodiment.

In the second embodiment, the light incident on the light receiving surface 18 of the monitor detector 17 is determined by the positioning of the components constituting the optical system in the optical pickup of the front monitor type as described above, during manufacturing or during assembly. The effect due to the variation in the light amount of the beam is reduced by adjusting at the time of assembling the optical system.

More specifically, the positions of the optical unit 1 and the beam splitter 10 constituting the optical system for the DVD disk 15 and the optical unit for the DVD disk 15 are interposed in the optical path of the light beam having a wavelength of 650 nm emitted from the DVD optical unit. First, the positions of the collimator lens 12, the dichroic filter 13, and the objective lens 14 are determined.

That is, after the arrangement of the optical system from the DVD optical unit 5 to the objective lens is determined, the 650 nm wavelength light beam emitted from the light source 6 of the CD optical unit 5 is applied to the signal recording surface of the CD disk 16. After being reflected at
The CD is diffracted by the diffraction grating 8 of the optical unit 5 so that the amount of diffracted light guided to the photodetector 7 is most appropriate.
The optical unit 5 is positioned.

Specifically, the optical unit 5 is moved in the direction 24 along the inner wall surface of the base (not shown) to
The optimum position is searched for and positioned while monitoring the signal corresponding to the amount of received light. After the optical unit 5 is positioned, the optical unit 5 is fixed with an adhesive and mechanically connected to the base.

Next, the monitor photodetector 17 is positioned in addition to the positioned optical system.

Specifically, along the inner wall surface of the base, direction 2
5, the monitor light detector 17 searches for and positions a position where the amount of light received by the light beam guided by the beam splitter 10 becomes optimal.

The optimum position of the monitor photodetector 17 is a position where the peak value of the light receiving amount of the light beam guided by the beam splitter 10 is obtained.

Here, the amount of light received by the monitor photodetector 17 and
FIG. 3 is a view for explaining the positional relationship of the monitor photodetector 17.
Is used.

FIG. 3 is a graph showing the relationship between the position of the monitor photodetector 17 in the direction 25 and the amount of received light.

In the graph of FIG. 3, the vertical axis indicates the amount of light received by the monitor photodetector 17 (no unit), and the horizontal axis indicates the position of the monitor photodetector 17 in the direction 25 (the unit is m).
m (millimeter) and the reference position is 0 mm).

According to this graph, the monitor photodetector 1
7 has a peak value of 1.0 at the reference position of 0 mm, and the level of the received light amount tends to decrease as the position of the monitor photodetector 17 deviates from this reference position in both the positive and negative directions.

As described above, the monitor photodetector 17
Since the peak value of the received light amount of the light beam guided by the beam splitter 10 is obtained at the reference position of 0 mm, in this case, the predetermined reference position is the optimum position where the monitor photodetector 17 should be disposed.

Therefore, the monitor photodetector 17 is located at this position.
Is positioned, and the monitor photodetector 17 is fixed at this position with an adhesive, and is mechanically connected to the base.

As described above, in the monitor photodetector 17, the position where the amount of the light beam guided by the beam splitter 10 is optimum is searched for and adjusted, and the light receiving surface 18 of the monitor detector 17 is adjusted. To reduce the influence of variations in the amount of light of the light beam incident on the light source.

Next, FIG. 4 is used to explain a third embodiment of the present invention.

FIG. 4 is a diagram showing an optical system according to the third embodiment of the present invention.

In the figure, an optical unit 1 having a diffraction grating 8, a light source 6, and a photodetector 7, an optical unit 5, a coupling lens 9, and a surface 20 on which a light beam of 650 nm wavelength emitted from the optical unit 1 is incident. The light is emitted from a beam splitter 10, a collimating lens 12, a dichroic filter 13, an objective lens 14, a monitor photodetector 17 including a light receiving unit 18, and a light source 2 in the optical unit 1,
The optical paths 19 of the light beams guided by the beam splitter 10 are all the same as the components constituting the optical system of the optical pickup in the first embodiment.

The DV to be reproduced or recorded is
The D disk 15 or the CD disk 16 is the same as that of the first embodiment.

In the third embodiment, of the above optical systems,
In the optical path of the light beam of 780 nm wavelength emitted from the light source 6,
Specifically, a １ ／ wavelength plate Lm is interposed between the beam splitter 10 and the coupling lens 9. 1 /
The two-wavelength plate Lm functions as a polarization direction changing unit that changes the polarization direction of the light beam incident from the light source 6.

On the surface 20 of the beam splitter 10,
The reflection characteristic of the light beam incident along the optical path 19 is set so that the reflection amount of the S-polarized wave (transverse wave) is larger than that of the P-polarized wave (longitudinal wave). The reflection characteristic of the polarized wave is determined according to the incident angle of light incident on the surface 20.

FIG. 5 is used to explain the relationship between the incident angle of the light beam and the reflectance.

FIG. 5 is a graph showing the relationship between the angle of incidence of a light beam on the surface 20 and the reflectance.

In this graph, the horizontal axis represents the incident angle, and the vertical axis represents the reflectance (unit:%).

In this graph, the broken line S on the surface 20 indicates the reflection characteristic of the S-polarized wave, and the broken line P indicates the reflection characteristic of the P-polarized wave.

In this embodiment, 78 light emitted from the light source 6
The light beam having a wavelength of 0 nm is a P-polarized wave (longitudinal wave).
The angle of incidence of the optical path 19 with respect to 0 is approximately 34 °.

Regarding the reflection characteristics of the surface 20, the reflectance of the S-polarized wave is somewhat high before and after the incident angle of 34 °, but the reflectance of the P-polarized wave is extremely low.

That is, it is shown that the light beam incident along the optical path 19 hardly obtains the amount of reflected light of the P-polarized wave.

Thus, in the present embodiment, the half-wave plate Lm is interposed in the optical path between the light source 6 and the beam splitter 10 to convert the light beam of the P-polarized light emitted from the light source 6 into an S-polarized wave. The light is changed and is incident on the surface 20 of the beam splitter 10, so that much reflected light is guided to the monitor photodetector 17.

As described above, in the beam splitter 10, the polarization characteristic of the incident light beam is polarized in accordance with the polarization characteristic of the surface 20 that reflects or transmits the light beam incident from the light source 6, thereby detecting the monitor light. The light amount of the light beam guided to the device 17 can be increased, and the light beam emitted from the light source 6 can be monitored with as high sensitivity as possible.

In this embodiment, the beam splitter 10
Since the reflection characteristic with respect to the incident angle of the light beam incident on the inner surface 20 is directed so that the S-polarized wave is reflected more, the polarization direction converting means interposed between the beam splitter 10 and the light source 6 is 1 / Although the two-wavelength plate Lm is used, it is important that the light reaching the signal recording surface of the optical disk is a circularly polarized wave.
A quarter-wave plate may be interposed instead of the half-wave plate Lm in accordance with the reflection characteristics of the beam.

If a sufficient light beam is incident on the monitor photodetector 17, monitoring can be performed with high sensitivity. Therefore, the light beam is reflected or transmitted in the beam splitter 10, and It is important to select a polarization direction conversion means in accordance with the polarization characteristics of the surface provided to guide the light.

Next, FIGS. 5 and 6 will be used to describe an optical disk drive equipped with an optical pickup having an optical system according to the first to third embodiments of the present invention.

FIG. 6 is a top view of an optical pickup incorporating the optical system of the present invention.

FIG. 7 is a top view of an optical disk drive equipped with an optical pickup.

FIG. 6A is a top view of the optical pickup Pu main body, and FIG. 6B is an enlarged view of the periphery of the beam splitter 10.

In FIG. 6, the optical pickup Pu has a die-cast base Db provided with an opening Om. Each component constituting the optical system according to the embodiment of the present invention is disposed in the opening Om of the base Db.

In the figure, 1 is a DVD optical unit, 2 is a light source built in the DVD optical unit 1, 5 is a CD optical unit, 6 is a light source built in the CD optical unit 5, 9 is a light source. A coupling lens 10 is a beam splitter, and 14 is an objective lens.

The objective lens 14 is supported so as to be movable in the radial direction of the disk to be reproduced. Other components constituting the optical system are fixed to the base Db by an adhesive, and mechanical parts are mounted on the base DB. Connected.

These are all the same as the components constituting the optical system shown in the first to third embodiments.
This optical system has a half-wave plate L as a component.
m may be interposed. The position where the half-wave plate is interposed is in the optical path between the light source 6 and the beam splitter 10 as shown in the third embodiment.

A guide rod receiving portion Rdh1 is provided on both sides of a base Db in which these optical systems are disposed in the opening Om so that a guide rod Rd having a circular cross section provided in the optical disk drive Drv can be inserted. , Rdh2.

As shown in the enlarged view of FIG. 6B, a light beam having a wavelength of 780 nm from the light source 6 enters the beam splitter 10 along the optical path 19 and is reflected on the surface 22 of the beam splitter 10. , Monitor photodetector 17
, The beam splitter 10 and the monitor photodetector 17 are arranged. The monitor detector 17 can generate a signal indicating the intensity of the light beam output from the light source 6 based on the light amount.

As shown in FIG. 7, the optical disk drive D
rv, the optical pickup Pu is connected to the guide rod R
The optical disc Od is guided in the radial direction Dr of the optical disc Od.

The optical disk drive Drv and the optical pickup Pu are connected to a flexible printed circuit board Fpc.
Are electrically connected via a connector Cnc.

On the other hand, the optical disk drive Drv has a turntable Tbl directly connected to a rotary motor (not shown).
Is provided, and on this turntable Tbl,
An optical disk Od can be placed and can be driven to rotate.

The optical disk Od is rotated by the turntable Tbl, and is moved by the guide rod Rd to a recording position of a digital signal for reproducing the optical pickup Pu or a position near the position where the digital signal is to be recorded. A digital signal can be recorded or reproduced on the signal recording surface of the optical disk by guiding and irradiating a light beam for reproduction or recording onto the signal recording surface of the optical disk via the optical disk.

In the first to third embodiments,
By guiding the light beam of the light source 6 from the beam splitter 10 to the monitor photodetector 17, the optical pickup Pu
The position where the monitor photodetector 17 is disposed can be set relatively freely, and the problem of the layout design of the optical system can be overcome. Also, a light beam for CD and DVD
The beam splitter 10, which guides the light beam to the objective lens 14, and the function of guiding the light beam of the light source 6 to the monitor photodetector 17 are additionally provided, so that the optical system occupying as little area as possible is provided. Can be realized.

[0126]

As described above, according to the present invention, it is possible to overcome the problem of layout design of an optical system including a monitor photodetector and other optical components, to realize an optical system having a small occupied area, A compact recording optical pickup and an optical disk drive can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing an optical system according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an optical system according to a second embodiment of the present invention.

FIG. 3 is a graph showing the relationship between the position of a monitor photodetector 17 and the amount of received light.

FIG. 4 is a diagram showing an optical system according to a third embodiment of the present invention.

FIG. 5 is a graph showing the relationship between the incident angle of a beam and the amount of reflected light.

FIG. 6 is a top view of an optical pickup incorporating the optical system of the present invention.

FIG. 7 is a top view of an optical disk drive device equipped with an optical pickup.

FIG. 8 is a diagram showing an optical system of an optical pickup according to the related art.

[Explanation of symbols]

 6 ... Light source 14 ... Objective lens 15, 16 ... Photodetector 17 ... Monitor photodetector 22 ... Optical parts

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01S 5/40 H01S 5/40

Claims (7)

[Claims] 1. An optical pickup for use in an optical disk drive for irradiating an optical disk with a light beam to record or reproduce a digital signal, comprising: a light source for emitting a light beam; An objective lens for guiding the signal beam onto the signal recording surface of the light beam;
Alternatively, the optical component includes an optical component that reflects the light and emits the light into the optical path, and a monitor light detector that monitors the intensity of the light beam. An optical pickup, which is arranged so as to be guided from a component to the monitor photodetector. 2. An optical pickup used in an optical disk drive for irradiating an optical disk with a light beam to record or reproduce a digital signal, comprising: a first light beam and a second light beam having mutually different wavelengths. A first light source and a second light source that emit light beams; an objective lens that guides the first light beam and the second light beam onto a signal recording surface of the optical disc; and the first light beam; An optical component to which a second light beam is incident, comprising a transmission surface that transmits the light beam or a reflection surface that reflects the light beam, and emitting the first light beam and the second light beam together; An optical component for guiding to an objective lens; and a monitor photodetector for monitoring the intensity of at least one of the first light beam and the second light beam. The light detector is characterized in that the light beam is disposed such that the light beam for monitoring the intensity is guided to the monitor light detector via a transmission surface or a reflection surface of the optical component. Optical pickup. 3. The reflection surface or the transmission surface has a polarization characteristic, and the light beam incident on the reflection surface or the transmission surface is polarized in advance according to the polarization characteristic of the reflection surface or the transmission surface. 3. An optical pickup according to claim 2, further comprising: a polarization direction changing means arranged so as to be arranged. 4. The optical pickup according to claim 2, further comprising a base to which said optical component, said first or second light source, and said monitor detector are mechanically connected. . 5. The monitor light detector is mechanically connected to the inner wall of the base, and is fixed after the amount of the light beam received is adjusted at the connection position. The optical pickup according to claim 2, wherein 6. The optical component, comprising: a first surface on which a light beam of a first wavelength is incident; a second surface on which a light beam of a second wavelength is incident; A third surface from which a light beam of a second wavelength is emitted, wherein the second surface is the first surface;
A part of the light beam of the wavelength is reflected and guided to the monitor photodetector, wherein the reflectance for the light beam of the first wavelength is the reflectance of the second surface for the first light beam. 3. The optical pickup according to claim 2, wherein the reflectance is higher than the reflectance of the first surface and the third surface. 7. An optical disk drive for irradiating an optical disk with a light beam to record or reproduce a digital signal, and emits a first light beam and a second light beam having mutually different wavelengths. A first light source and a second light source, an objective lens for guiding the first light beam and the second light beam onto a signal recording surface of the optical disc, and the first light beam;
An optical component to which a second light beam is incident, the optical component having a transmission surface that transmits the light beam or a reflection surface that reflects the light beam, and emitting both the first light beam and the second light beam, An optical component for guiding to the objective lens; and a monitor light detector for monitoring the intensity of at least one of the first light beam and the second light beam, wherein the optical component and the monitor light detection The device, the light beam or the transmission surface of the optical component,
An optical pickup, which is arranged so that the light beam for monitoring the intensity is guided to the monitor photodetector through a reflection surface, and a turntable on which the disc is placed and driven to rotate, An optical disk drive, comprising: a guide for guiding the optical pickup in a radial direction of the optical disk.