JP2003006915A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove noise from a laser light source in an optical disk device. SOLUTION: The optical disk device is equipped with a laser light source for outputting a laser beam, a polarizing beam splitter for branching a laser beam from the laser light source into a first optical beam for reproducing information recorded on an optical disk and a second light beam for canceling noise from the laser light source, and a reproducing signal light receiver for receiving a return light beam from the information recording face of the optical disk to form a reproducing signal. The device is designed to use the laser-light- source-noise canceling signal obtained by the second light beam and to carry out a noise canceling arithmetic operation for the purpose of removing noise contained in the reproducing signal from the light receiver. In this optical disk device, the second light beam is received by the reproducing signal light receiver. An optical spot by the second light beam is emitted to a different position, compared with an optical spot by the first light beam, on the light receiving area of the light receiver.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc apparatus for reproducing information by irradiating an optical disc with a laser beam, and more particularly to a technique for removing a noise component caused by a variation of the laser beam from a reproduced signal. .

[0002]

2. Description of the Related Art In recent years, the recording density of information on optical discs has become higher and the S / N required for reproducing the information has increased accordingly.
It is difficult to secure the ratio (signal to noise ratio). The reproduced signal obtained by irradiating the optical disk with the laser light contains various noise components. The noise included in the reproduced signal can be classified into the following three types by focusing on the generation factor.

(1) Disk noise due to surface roughness or variation of the optical disk (2) Circuit system noise generated in a circuit including a light receiver and an amplifier (3) Laser light source due to a laser diode (LD) which is a light source Noise (LD noise)

The circuit system noise includes photodetector (PD) amplifier noise that depends on the design of the first-stage amplifier of the photodetector, shot noise caused by fluctuations of electrons in the photodetection current of the photodetector, and first-stage current-voltage conversion amplifier of the photodetector. There is thermal noise (thermal noise) due to the conversion resistance of the.

Laser light source noise is noise caused by fluctuations in the wavelength and power of laser light, and is caused by transitions in the light emission mode caused by temperature changes, return light, and the like. The most dominant of these is quantum noise due to fluctuations of electrons in the current flowing through the laser diode.

In recent years, techniques for removing noise from laser light sources have been developed. The optical disc apparatus includes a light source for receiving a return light from the optical disc and generating a reproduction (RF) signal and a reproduction signal light receiver and a laser light source to generate an automatic power control (APC) signal. A monitor light receiver is provided. A laser light source noise cancel (LNC) signal is taken out from the light source monitor light receiver to remove the laser light source noise included in the reproduction signal.

A conventional device and method for removing noise from a laser light source will be described with reference to FIG. This example is disclosed in Japanese Patent Application Laid-Open No. 10-12 / 98 filed on Oct. 18, 1996 by the same application as the applicant of the present application.
This is disclosed in Japanese Patent No. 4919. For details, refer to the same publication.

As shown in the figure, the optical system of the optical disk device of this example includes a laser diode 11 as a light source, a collimator lens 12, a polarization beam splitter 13, a quarter wavelength plate 14, an objective lens 15, and a condenser lens 16. It has a reproduction signal light receiver 17 and a light source monitor light receiver 18. The laser light from the laser diode 11 is collimator lens 12
Is converted into parallel rays by and is split into two by the polarization beam splitter surface 13A of the polarization beam splitter 13. One of the split lights is deflected by the polarization beam splitter surface 13A, and is received by the light source monitor light receiver 18. The other branched light passes through the polarization beam splitter surface 13A and reaches the information recording surface of the optical disc 20 via the quarter-wave plate 14 and the objective lens 15. The light from the information recording surface of the optical disc is deflected by the polarization beam splitter surface 13A of the polarization beam splitter 13, passes through the condenser lens 16, and is received by the reproduction signal light receiver 17.

The output signal of the light source monitor photodetector 18 should have a level fluctuation corresponding to the fluctuation of the wavelength and power of the laser light. That is, the output signal of the light source monitor light receiver 18 should have the same phase as the laser light source noise included in the output signal of the reproduction signal light receiver 17. Therefore, the laser light source noise is removed from the reproduction signal by canceling the output signal of the light source monitoring light receiver 18 from the output signal of the reproduction signal light receiver 17.

An example of the cancel calculation will be described. The output signal of the reproduction signal light receiver 17 is supplied to the adder via the current-voltage converter and the amplifier. Light receiver for light source monitor 18
The output signal of 1 is passed through the current-voltage converter and the amplifier, the phase is inverted by the phase inverter, and the result is supplied to the adder.
As the output of the adder, a reproduction signal from which laser light source noise is removed is obtained.

[0011]

In the above example, the laser light source noise cancellation (LNC) signal is reproduced (RNC).
F) generated by a receiver and circuit different from the signal. Therefore, a delay error inevitably occurs between the laser light source noise cancellation signal and the reproduction signal. The delay error degrades or limits the laser light source noise cancellation performance. For example, when the delay error is T time, the maximum noise cancellation amount is represented by the following equation.

[0012]

[ ^Equation 1] Cmax = 1 + e ^-jwT

Factors of the delay error include a difference in group delay characteristics due to process variations of integrated circuits used for the two photodetectors, an optical path difference of light received by the two photodetectors, and the like. For example, in order to obtain a noise cancellation amount of 5 dB in the signal band of 30 MHz, the delay error between two signals must be within 3 ns (nanosecond). The delay error due to the difference in group delay characteristics due to process variations is about 2 ns (nanosecond),
The delay error due to the optical path difference is about 1 ns (nanosecond).
Therefore, in the above example, it is possible to obtain a noise cancellation amount of 5 dB in the signal band of 30 MHz.

However, for example, in order to obtain a noise cancellation amount of 10 dB in the signal band of 100 MHz, the delay error between the two signals must be within 0.5 ns (nanosecond). This cannot be achieved in the above example. This is because the delay error due to the optical path difference is constant and can be corrected in a circuit manner, but the delay error due to the process variation cannot be corrected.

Therefore, it is an object of the present invention to provide an optical disk device capable of minimizing a delay error between a reproduction signal and a laser light source noise cancellation signal.

According to the present invention, in a wide band including a high frequency,
An object of the present invention is to provide an optical disc device that can obtain high laser light source noise canceling performance.

[0017]

According to the present invention, a laser light source for outputting laser light, a first light beam for reproducing information recorded on an optical disk, and a laser light source for canceling laser light from the laser light source are used. A beam splitter for splitting the beam into a second light beam and a light receiver for receiving a return light beam from the information recording surface of the optical disc to generate a reproduction signal. In the optical disk device configured to perform the noise canceling operation to remove the noise included in the reproduction signal from the photodetector using the obtained laser light source noise canceling signal, the second light beam is the received light. The laser light source noise canceling signal is generated separately and simultaneously with the reproduction signal by irradiating the container. There.

According to the present invention, since the reproduction (RF) signal beam and the laser light source noise cancellation (LNC) signal beam are received by the same light receiver, the delay error between the reproduction signal and the laser light source noise cancellation signal is minimized. Can be converted.

In an example of the present invention, the second light beam is spatially separated from the first light beam by a reflecting surface inclined with respect to a plane perpendicular to the optical axis of the polarization beam splitter, The light spot of the second light beam is configured to be irradiated on the light receiving surface of the light receiver at a position different from the light spot of the first light beam.

In another example of the present invention, the second light beam is optically separated from the first light beam by a polarization beam splitter surface arranged in front of the light receiver,
The light spot of the second light beam is configured to be irradiated on the light receiving surface of the light receiver at a position different from the light spot of the first light beam.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION An example of an optical disk device according to the present invention will be described below with reference to FIGS. 1 to 1
5 shows only the configuration of the optical system which is the main part of the optical disk device of the present invention. The same components as those of the conventional optical disk device shown in FIG. 16 are designated by the same reference numerals, and detailed description thereof will be omitted.

According to the present invention, the reproduction (RF) signal beam and the laser light source noise cancellation (LNC) signal beam are received by the same light receiver. Therefore, the delay error between the reproduction signal and the laser light source noise cancellation signal can be minimized. Moreover, since the delay error can be minimized, the noise canceling performance can be obtained in a wide band. The beam for the automatic power control (APC) signal may be received by the same light receiver, but may be received by different light receivers.

A first example of the optical disk device of the present invention will be described with reference to FIG. The optical system of the optical disk device of this example includes a laser diode 11 as a light source, a collimator lens 12, a polarization beam splitter 13, a quarter-wave plate 1
4, an objective lens 15, a condenser lens 16, and a light receiver 17. The light receiver 17 is used both for the reproduction signal and for the laser light source noise cancellation signal. Polarizing beam splitter 13
Has a polarization beam splitter surface 13A and a total reflection surface 31.

The optical disk device of the present embodiment is different from the conventional optical disk device shown in FIG. 16 in that the light source monitor light receiver 18 is not provided and that the polarization beam splitter 1 is used.
3 is different in that a total reflection surface 31 is provided, and other configurations may be the same. Polarizing beam splitter 1
The total reflection surface 31 of 3 is slightly inclined with respect to the surface perpendicular to the optical path.

The polarization beam splitter surface 13A of the polarization beam splitter 13 totally reflects S-polarized light, for example.
It may be set to transmit 90% of the polarized light and reflect 10% of the P polarized light.

The laser light from the laser diode 11 is collimated by the collimator lens 12. In this example, the laser diode 11 mainly generates P-polarized light. This P-polarized light is split into two by the polarization beam splitter surface 13A. 10% of the P-polarized light is deflected by the polarization beam splitter surface 13A and reflected by the total reflection surface 31, 90% of the reflected light passes through the polarization beam splitter surface 13A, and passes through the condenser lens 16 and the light receiver 17 Is received by. On the other hand, 90% of the P-polarized light passes through the polarization beam splitter surface 13A and reaches the information recording surface of the optical disc 20 via the quarter-wave plate 14 and the objective lens 15. Return light from the information recording surface of the optical disc is converted into S-polarized light by passing through the quarter-wave plate 14.
100% of this S-polarized light is deflected by the polarization beam splitter surface 13A of the polarization beam splitter 13 and is received by the reproduction signal light receiver 17 via the condenser lens 16.

As described above, the polarization beam splitter 13
Since the total reflection surface 31 is inclined, the reflected light is displaced from the optical axis of the light receiver 17 as shown in the figure. The return light from the information recording surface of the optical disc and the light reflected by the total reflection surface 31 of the polarization beam splitter 13 are spatially separated in this way, and are irradiated to different positions on the light receiving surface of the light receiver 17.
Therefore, it is possible to obtain the reproduction signal by the return light from the information recording surface of the optical disk and the laser light source noise canceling signal by the light reflected by the total reflection surface 31 of the polarization beam splitter 13 simultaneously and separately.

By changing the inclination angle of the total reflection surface 31, the distance between the light spot for the reproduction signal and the light spot for the laser light source noise cancellation signal on the light receiving surface of the light receiver 17 changes. By changing the inclination angle of the total reflection surface 31, the distance between the two light spots can be set to an optimum value. It should be noted that 10% of the light reflected by the total reflection surface 31 of the polarization beam splitter 13 and reaching the polarization beam splitter surface 13A is deflected in the direction of the laser diode 11 without passing through the polarization beam splitter surface 13A, so-called stray light. Become. However, since the total reflection surface 31 is inclined with respect to the plane perpendicular to the optical axis, the stray light does not reach the laser diode 11. In this example, automatic power control (APC)
A laser light source noise canceling signal may be used as the signal.

A second example of the present invention will be described with reference to FIG. The optical disc device of this example is different from the first example shown in FIG. 1 in that the total reflection surface 31 of the polarization beam splitter 13 is different.
The beam splitting element 32 such as a grating or a hologram element is arranged on the inner surface of the. The light reflected by the total reflection surface 31 of the polarization beam splitter 13 passes through the beam splitter 32 and is spatially split into two lights. Two
The two lights are applied to different positions on the light receiving surface of the light receiver 17. Therefore, the total reflection surface 3 of the polarization beam splitter 13 is
Laser light source noise canceling signal and automatic power control (APC) from the light reflected by 1.
The signals can be obtained simultaneously and separately.

A third example of the present invention will be described with reference to FIG. The optical disc device of this example is different from the first example shown in FIG. 1 in that the total reflection surface 31 of the polarization beam splitter 13 is different.
Instead of, the beam splitter surface 33 is arranged, and
An automatic power control (APC) signal light receiver 34 is provided behind the beam splitter surface 33. This beam splitter surface 33 is, for example,
It reflects 50% and transmits 50% of P-polarized light. The light reflected by the beam splitter surface 33 is received by the light receiver 17, and a laser light source noise cancellation signal is generated. The light transmitted through the beam splitter surface 33 is received by an automatic power control (APC) signal light receiver 34, and an automatic power control (APC) signal is generated.

A fourth example of the present invention will be described with reference to FIG. The optical disc device of this example is different from the first example shown in FIG. 1 in that the light receiver 17 is arranged in parallel to the optical axis of the condenser lens 16 and in front of the light receiver 17. Is provided with a second polarization beam splitter 35. The second polarization beam splitter 35 has a polarization beam splitter surface 35A and a total reflection surface 35B that are arranged, for example, at an angle of 45 degrees with respect to the optical path. The polarization beam splitter surface 35A transmits 100% of S-polarized light and reflects 100% of P-polarized light.

The S-polarized light, which is the return light from the information recording surface of the optical disk, passes through the condenser lens 16, passes through the polarization beam splitter surface 35A of the second polarization beam splitter 35, and is reflected by the total reflection surface 35B. Then, the light is received by the light receiver 17, and a reproduction signal is generated. The P-polarized light, which is the reflected light from the total reflection surface 31, passes through the condenser lens 16 and passes through the polarization beam splitter surface 35 of the second polarization beam splitter 35.
A is reflected and received by the light receiver 17, and the laser light source noise canceling signal and the automatic power
A control (APC) signal is generated.

In this example, the second polarization beam splitter 3
Since the laser beam noise canceling light beam is separated from the reproduction signal light beam by the polarization beam splitter surface 35A of No. 5, the total reflection surface 31 of the first polarization beam splitter 13 may be arranged perpendicular to the optical axis. . Of course,
The total reflection surface 31 of the first polarization beam splitter 13 is shown in FIG.
The laser light source noise canceling light beam may be spatially separated from the reproduction signal light beam by inclining similarly to the above example.

A fifth example of the present invention will be described with reference to FIG. The optical disc device of this example is different from the fourth example shown in FIG. 4 in that the light receiver 17 is arranged perpendicularly to the optical axis of the condenser lens 16 and in front of the light receiver 17. Is provided with the second polarization beam splitter 36. The second polarization beam splitter 36 has a polarization beam splitter surface 36A, a beam splitter surface or a half mirror 35B, and a total reflection surface 35C that are arranged, for example, at an angle of 45 degrees with respect to the optical path. The polarization beam splitter surface 36A is for a laser light source noise cancellation signal,
The beam splitter surface 36B is for the reproduction signal, and the total reflection surface 36
C is automatic power control (APC)
For signals. The polarization beam splitter surface 36A transmits 100% of S-polarized light and reflects 100% of P-polarized light.
The beam splitter surface 36B reflects, for example, 80% of S-polarized light and transmits 20% thereof. According to this example, the laser light source noise cancellation signal light spot, the reproduction signal light spot, and the automatic power control (AP
C) The signal light spots appear at different positions on the light receiving surface of the light receiver 17. Therefore, three signals can be extracted simultaneously and separately.

A sixth example of the present invention will be described with reference to FIG. The optical disc device of this example is different from the fifth example shown in FIG. 5 in that the second polarization beam splitter 36 is provided with a polarization beam splitter surface 36A and a beam splitter in which the second polarization beam splitter 36 is inclined at 45 degrees with respect to the optical path. Face or half mirror 3
6B, and further, an automatic power control (APC) signal light receiver 37 is provided as a second light receiver. According to this example, the laser light source noise cancellation signal and the reproduction signal are obtained by the first light receiver 17, and the automatic power control (AP
C) The signal is obtained by the second light receiver 37.

A seventh example of the present invention will be described with reference to FIG. The optical disc apparatus of this example is different from the sixth example shown in FIG. 6 in that condenser lenses 16 and 38 are provided immediately in front of the two light receivers 17 and 37, respectively.

In the examples of FIGS. 5, 6 and 7, the polarization beam splitter surface 36A of the second polarization beam splitter 36 is used.
In order to separate the laser light source noise canceling light beam from the reproduction signal light beam, the total reflection surface 31 of the first polarization beam splitter 13 may be arranged perpendicular to the optical axis. Of course, the total reflection surface 31 of the first polarization beam splitter 13 may be tilted as in the example of FIG. 1 to spatially separate the laser light source noise canceling light beam from the reproduction signal light beam.

An eighth example of the present invention will be described with reference to FIG. The optical disc device of this example is different from the first example shown in FIG. 1 in that the polarization beam splitter surface 13A of the polarization beam splitter 13 transmits 100% of P-polarized light and reflects 100% of S-polarized light. Being configured. In this example, a half-wave plate 39 is further provided between the laser diode 11 and the polarization beam splitter 13, and a second quarter-wave plate 40 is provided inside the total reflection surface 31 of the polarization beam splitter 13. It is provided. Instead of the half-wave plate 39, the polarization beam splitter 13
Means for adjusting the polarization plane of the light incident on the laser diode, for example, a rotation mechanism 39A for rotating the laser diode 11 around the optical axis.
May be used.

The light from the laser diode 11 becomes light containing P-polarized light and S-polarized light at a predetermined ratio by passing through the half-wave plate 39 and the polarization plane adjusting means. The P-polarized component of this light passes through the polarization beam splitter surface 13A of the polarization beam splitter 13 and reaches the optical disc 20. The S-polarized component of this light is the polarization beam splitter 1
It reflects the polarization beam splitter surface 13A of No. 3 and reaches the total reflection surface 31. The return light from the information recording surface of the optical disk passes through the first quarter-wave plate 14 to become P-polarized light and S-polarized light, and is reflected by the polarization beam splitter surface 13A of the polarization beam splitter 13 and reaches the light receiver 17. To do. In this way, a reproduction signal is generated by the light receiver 17. The S-polarized light reflected by the total reflection surface 31 is the second quarter wave plate 40.
To become P-polarized light, pass through the polarization beam splitter surface 13A of the polarization beam splitter 13, and pass through the light receiver 17
To reach. The photoreceiver 17 generates a laser light source noise cancellation signal and an automatic power control (APC) signal. As in the second example of FIG. 2, in this example, a beam splitter is provided inside the total reflection surface 31 to generate a laser light source noise canceling signal beam and an automatic power control (APC) signal beam. It may be spatially separated and generated separately.

A ninth example of the present invention will be described with reference to FIG. The optical disc apparatus of this example is different from the first example shown in FIG. 1 in that the collimator lens 12 is not provided between the laser diode 11 and the polarization beam splitter 13, but instead of the objective lens 15 and the quarter-wave plate 14. The total reflection surface 41 provided in the polarization beam splitter 13 has a lens function or a parallel light conversion function.

Similar to the first example of FIG. 1, the polarization beam splitter surface 13A of the polarization beam splitter 13 totally reflects S-polarized light and transmits 90% of P-polarized light and P-polarized light, respectively.
It may be set to reflect 10% of the polarization.

The laser diode 11 mainly generates P-polarized light in this example. This P-polarized light is split into two by the polarization beam splitter surface 13A. P-polarized 1
0% is deflected by the polarization beam splitter surface 13A, reflected by the total reflection surface 31, converted into parallel rays by the lens function of the total reflection surface 31, and 90% of the rays converted into parallel rays.
Passes through the polarization beam splitter surface 13A, passes through the condenser lens 16, and is received by the light receiver 17. On the other hand, 90% of the P-polarized light passes through the polarization beam splitter surface 13A, passes through the quarter-wave plate 14, is collimated by the collimator lens 12, and passes through the objective lens 15 to the information recording surface of the optical disc 20. To reach. Light from the information recording surface of the optical disk is converted into S-polarized light by passing through the quarter-wave plate 14. 100% of this S-polarized light
Is deflected by the polarization beam splitter surface 13A of the polarization beam splitter 13 and is received by the reproduction signal light receiver 17 via the condenser lens 16.

A tenth example of the present invention will be described with reference to FIG. The optical disc device of this example is different from the third example shown in FIG. 3 in that the first collimator lens 12 is disposed between the objective lens 15 and the quarter-wave plate 14. The collimator lens 42 of the above is arranged in front of the automatic power control (APC) signal light receiver 34, and the polarization beam splitter 13
The polarized beam splitter surface 43 provided in the above has a lens function or a parallel light beam conversion function. The polarization beam splitter surface 43 is, for example, as in the third example of FIG.
It reflects 50% and transmits 50% of P-polarized light.

An eleventh example of the present invention will be described with reference to FIG. The optical disc apparatus of this example is different from the fourth example shown in FIG. 4 in that the collimator lens 12 is an objective lens 1
5 and the quarter-wave plate 14, and the total reflection surface 4 provided on the polarization beam splitter 13.
1 has a lens function or a parallel light beam conversion function.

A twelfth example of the present invention will be described with reference to FIG. The optical disc device of this example is different from the fifth example shown in FIG. 5 in that the collimator lens 12 is an objective lens 1
5 and the quarter-wave plate 14, and the total reflection surface 4 provided on the polarization beam splitter 13.
1 has a lens function or a parallel light beam conversion function.

A thirteenth example of the present invention will be described with reference to FIG. The optical disc device of this example is different from the sixth example shown in FIG. 6 in that the collimator lens 12 is an objective lens 1
5 and the quarter-wave plate 14, and the total reflection surface 4 provided on the polarization beam splitter 13.
1 has a lens function or a parallel light beam conversion function.

A fourteenth example of the present invention will be described with reference to FIG. The optical disc apparatus of this example is different from the seventh example shown in FIG. 7 in that the collimator lens 12 is the objective lens 1
5 and the quarter-wave plate 14, and the total reflection surface 4 provided on the polarization beam splitter 13.
1 has a lens function or a parallel light beam conversion function.

A fifteenth example of the present invention will be described with reference to FIG. The optical disc apparatus of this example is different from the eighth example shown in FIG. 8 in that the collimator lens 12 is an objective lens 1
5 and the quarter-wave plate 14, and the total reflection surface 4 provided on the polarization beam splitter 13.
1 has a lens function or a parallel light beam conversion function.

Although the example of the present invention has been described above, the present invention is not limited to the above example, and various other examples are possible within the scope of the invention described in the claims. It will be easily understood by those skilled in the art.

[0050]

According to the present invention, since the reproduction (RF) signal beam and the laser light source noise cancellation (LNC) signal beam are received by the same light receiver, the reproduction signal and the laser light source noise cancellation signal are received. There is an effect that the delay error can be minimized.

According to the present invention, since the delay error between the reproduction signal and the laser light source noise canceling signal can be minimized, the noise canceling performance can be obtained in a wide band.

According to the present invention, by merely changing the inclination angle of the total reflection surface or the polarization beam splitter surface provided on the polarization beam splitter, the reproduction signal beam spot and the laser light source noise canceling signal on the light receiving surface of the light receiver can be obtained. There is an effect that the distance between the beam spots can be changed.

[Brief description of drawings]

FIG. 1 is an explanatory diagram for explaining a first example of an optical system of an optical disc device of the present invention.

FIG. 2 is an explanatory diagram for explaining a second example of the optical system of the optical disc device of the present invention.

FIG. 3 is an explanatory diagram for explaining a third example of the optical system of the optical disc device of the present invention.

FIG. 4 is an explanatory diagram for explaining a fourth example of the optical system of the optical disc device of the present invention.

FIG. 5 is an explanatory diagram for explaining a fifth example of the optical system of the optical disc device of the present invention.

FIG. 6 is an explanatory diagram for explaining a sixth example of the optical system of the optical disc device of the present invention.

FIG. 7 is an explanatory diagram for explaining a seventh example of the optical system of the optical disc device of the present invention.

FIG. 8 is an explanatory diagram for explaining an eighth example of the optical system of the optical disc device of the present invention.

FIG. 9 is an explanatory diagram for explaining a ninth example of the optical system of the optical disc device of the present invention.

FIG. 10 is an explanatory diagram for explaining a tenth example of the optical system of the optical disc device of the present invention.

FIG. 11 is an explanatory diagram for explaining an eleventh example of the optical system of the optical disc device of the present invention.

FIG. 12 is an explanatory diagram for explaining a twelfth example of the optical system of the optical disc device of the present invention.

FIG. 13 is an explanatory diagram for explaining a thirteenth example of the optical system of the optical disc device of the present invention.

FIG. 14 is an explanatory diagram for explaining a fourteenth example of the optical system of the optical disc device of the present invention.

FIG. 15 is an explanatory diagram for explaining a fifteenth example of the optical system of the optical disc device of the present invention.

FIG. 16 is an explanatory diagram for explaining an example of an optical configuration of a conventional optical disc device.

[Explanation of symbols]

11 ... Laser diode, 12 ... Collimator lens, 13 ... Polarization beam splitter, 13A ... Polarization beam splitter surface, 14 ... Quarter wave plate,
15 ... Objective lens, 16 ... Condensing lens, 17 ...
.Received signal light receiver, 18 ... Light source monitor light receiver,
20 ... Optical disc, 31 ... Total reflection surface, 32 ...
Beam splitter, 33 ... Polarizing beam splitter surface, 34 ... Photoreceiver, 35 ... Polarizing beam splitter, 35A ... Polarizing beam splitter surface, 35B ...
-Total reflection surface, 36 ... Polarizing beam splitter, 36
A ... Polarizing beam splitter surface, 36B ... Beam splitter surface, 36C ... Total reflection surface, 37 ... Photoreceiver, 38 ... Condensing lens, 39 ... Half wave plate, 40 ... Quarter wave plate, 41 ... Total reflection surface,
42 ... Collimator lens, 43 ... Polarizing beam splitter surface

Claims (3)

[Claims] 1. A laser light source for outputting a laser light, and a laser light from the laser light source is branched into a first light beam for reproducing information recorded on an optical disk and a second light beam for canceling noise from the laser light source. A beam splitter for generating a reproduction signal by receiving a return light beam from the information recording surface of the optical disc, and a laser light source noise canceling signal obtained by the second light beam. In an optical disc device configured to perform a noise canceling operation to remove noise included in a reproduction signal from the photodetector, the reproduction is performed by irradiating the photodetector with the second light beam. An optical disc characterized in that the laser light source noise canceling signal is generated separately and simultaneously with the signal. Apparatus. 2. The optical disk device according to claim 1, wherein the second light beam is spatially separated from the first light beam by a reflecting surface inclined with respect to a surface perpendicular to the optical axis of the beam splitter. The optical disc is characterized in that the optical spot of the second light beam is irradiated onto a position different from the light spot of the first light beam on the light receiving surface of the light receiver. apparatus. 3. The optical disk device according to claim 1, wherein the second light beam is optically separated from the first light beam by a polarization beam splitter surface arranged in front of the light receiver. An optical disk device, wherein the light spot of the second light beam is configured to be irradiated on a position different from the light spot of the first light beam on the light receiving surface of the light receiver.