JP4095887B2 - Optical pickup device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical pickup device mounted on an optical information recording / reproducing device such as an optical disk drive device or an optical card device.
[0002]
[Prior art]
As a general configuration example of a conventional optical pickup device, the one described in Patent Document 1 can be exemplified.
[0003]
The schematic configuration of the optical system in the optical pickup device will be described below with reference to FIG.
[0004]
In FIG. 1, a light beam from a semiconductor laser 1 is collimated by a collimator lens 2, passes through a polarization beam splitter 3 that is a polarization separation element as P-polarized light, and is circularly polarized by a λ / 4 plate 4 that is a wavelength plate. Then, the optical disk 6 is irradiated through the objective lens 5, and the reflected light from the optical disk 6 is reflected by the polarization beam splitter 3 through the objective lens 5 and the λ / 4 plate 4 to receive the light. 7 is received, and the light receiving element 7 is configured to obtain control data at the time of recording / reproducing with respect to the optical disc 6.
[0005]
[Patent Document 1]
JP-A-8-273172 [0006]
[Problems to be solved by the invention]
In the conventional optical pickup device, the incident angle (disc incident angle) of the light beam of the semiconductor laser 1 with respect to the optical disc 6 changes due to the phase difference of the optical disc 6, and the reflected light from the optical disc 6 returns to the semiconductor laser 1. (See FIG. 2), or the amount of light received by the light receiving element 7 decreases (see FIG. 3).
[0007]
That is, the optical disc 6 can be considered as a uniaxial anisotropic refractive index ellipsoid whose optical anisotropy has a principal axis in the thickness direction, and the difference Δ between the refractive index for the extraordinary ray and the refractive index for the extraordinary ray of the optical disc 6. Is 0.0006 and the thickness t of the optical disk 6 is 1.2 mm, the relationship between the disk incident angle of the light beam from the semiconductor laser 1 incident on the optical disk 6 and the return light to the semiconductor laser 1 is shown in FIG. It becomes the relationship shown. Thus, if there is a return light to the semiconductor laser 1, the kink level of the semiconductor laser 1 is lowered, and the recording quality on the optical disc 6 is remarkably lowered.
[0008]
The relationship between the angle of the light beam incident on the optical disk 6 (disk incident angle) and the amount of received light received by the light receiving element 7 is as shown in FIG. 3 is an area where there are many push-pull signals, the quality of the track error signal and the address signal is lowered, and the recording quality on the optical disk 6 is significantly lowered.
[0009]
SUMMARY OF THE INVENTION An object of the present invention is to provide an optical pickup device that solves the conventional problems and can stabilize the recording quality on an optical disc without degrading the quality of a track error signal and an address signal. .
[0010]
[Means for Solving the Problems]
In order to achieve the object, the invention according to claim 1 irradiates the optical disk with a light beam from a semiconductor laser through a polarization separation element, a wave plate, and an objective lens, and reflects the reflected light from the optical disk with the light beam. in the objective lens, the wave plate, the optical pickup device configured to be incident on the light receiving element through the polarization separating element, when synthesized the phase difference in said optical disc and the wavelength plate, meets the following formula (formula 1), and The phase difference is set so as to decrease concentrically as it goes from the central portion to the outer peripheral portion of the wave plate .
[0011]
(Equation 1)
(1/4 + n) λ
However, λ is the wavelength of the semiconductor laser, n is 0 or an integer. With the above configuration, the return light to the semiconductor laser is 0, and the amount of light received by the light receiving element can receive 100% of the reflected light from the optical disk. Thus, since no light returns to the semiconductor laser, the kink level of the semiconductor laser is not lowered, and the recording quality on the optical disk is stabilized. Further, the push-pull signal can be prevented from being lowered, the quality of the track error signal and the address signal is not lowered, and the good signal detection as described above is easily performed by the light receiving element according to the change of the disk incident angle. This makes it possible to stabilize the recording quality on the optical disc.
[0012]
The invention according to claim 2 irradiates the optical disk with a light beam from a semiconductor laser through a polarization separation element, a wave plate, and an objective lens, and reflects the reflected light of the light beam from the optical disk to the objective lens, the wave plate, the optical pickup device configured to be incident on the light receiving element through the polarization separating element, when the phase difference Φ in the wavelength plate, meets the following formula (formula 2), and a central portion of the phase difference is the wave long plate It is characterized by being set so as to become concentrically smaller as it goes from the outer periphery to the outer periphery .
[0013]
(Equation 2)
nλ <Φ <(1/4 + n) λ
However, λ is the wavelength of the semiconductor laser, n is 0 or an integer. With the above configuration, it is possible to use a normal inexpensive wavelength plate such as a λ / 6 plate. The signal quality is not deteriorated, and the good signal detection as described above can be easily performed by the light receiving element according to the change of the disc incident angle, and the recording quality on the optical disc is stabilized.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0017]
The basic structure of the optical system in the embodiment of the optical pickup device of the present invention is the same as that shown in FIG. 1, and members corresponding to those already described are assigned the same reference numerals and detailed description thereof is omitted.
[0018]
A first embodiment of the present invention will be described with reference to FIG.
[0019]
The light beam from the semiconductor laser 1 is collimated by the collimator lens 2, passes through the polarization beam splitter 3, which is a polarization separation element, as P-polarized light, and is irradiated onto the optical disk 6 through the wave plate 4 and the objective lens 5. . The reflected light from the optical disk 6 is reflected by the polarization beam splitter 3 through the objective lens 5 and the wave plate 4 and enters the light receiving element 7.
[0020]
In the first embodiment, the phase difference of the wave plate 4 is set so that the phase difference in the wave plate 4 is (1/4 + n) λ when the phase difference between the wave plate 4 and the optical disk 6 is combined ((1/4 + n)) ( Where λ is the wavelength in the emitted light beam of the semiconductor laser, and n is 0 or an integer). By setting in this way, the return light to the semiconductor laser 1 becomes 0, and the light amount received by the light receiving element 7 can receive 100% of the reflected light from the optical disk 6.
[0021]
For this reason, in the first embodiment, since no light returns to the semiconductor laser 1, there is no decrease in the kink level of the semiconductor laser 1, and the recording quality on the optical disc 6 is stabilized. Further, it is possible to prevent the push-pull signal from being lowered, the quality of the track error signal and the address signal is not lowered, and the recording quality to the optical disc 6 is stabilized.
[0022]
In the second embodiment of the present invention, the phase difference Φ in the wave plate 4 is selected in the range of nλ <Φ <(1/4 + n) λ (where λ is the wavelength in the emitted light beam of the semiconductor laser, and n is 0 or (Integer). By this selection, for example, the amount of light received by the light receiving element 7 when the phase difference Φ in the wave plate 4 is set to λ / 6 is as shown in FIG. 4, and the push-pull signal at a disk incident angle of 20 ° to 30 ° is obtained. It becomes possible to detect efficiently.
[0023]
Therefore, in the second embodiment, it is possible to use a normal inexpensive wave plate (λ plate) such as a λ / 6 plate, for example, and the quality of the track error signal and the address signal is not deteriorated. The recording quality is stable.
[0024]
FIG. 5 is a configuration diagram of a wave plate that can be used in the present embodiment. In the wave plate 4, the phase difference in the wave plate 4 is λ / 4 at the central portion, λ / 8 at the outermost peripheral portion, and the middle. In the portion, the phase difference is set to be λ / 5 to λ / 6, that is, the phase difference is reduced toward the outer peripheral portion. By setting in this way, as shown in FIG. 6, it is possible to reduce the influence of the amount of light received by the light receiving element 7 due to the disk incident angle.
[0025]
By using the wave plate having the configuration shown in FIG. 5, the return light to the semiconductor laser 1 can be made substantially zero, and the amount of light received by the light receiving element 7 can be made almost 100% of the reflected light from the optical disk 6. become. Thus, by light back to the semiconductor laser 1 is little, there is no decrease in kink level of the semiconductor laser 1, the recording quality of the optical disk 6 is stabilized, also possible to prevent a decrease in push-pull signal Thus, the quality of the track error signal and the address signal is not deteriorated, and the recording quality on the optical disc 6 is stabilized.
[0026]
【The invention's effect】
As described above, according to the optical pickup device of the present invention, the return light to the semiconductor laser can be eliminated, and hence the kink level in the semiconductor laser can be eliminated. Since the quality of the track error signal and the address signal is not deteriorated and the light receiving element changes according to the change in the incident angle of the disc , the above-mentioned good signal detection is possible. Can be easily implemented, and the recording quality onto the optical disk can be stabilized.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an optical system in an optical pickup device for explaining an embodiment of the present invention. FIG. 2 is a diagram showing a relationship between a semiconductor laser and a disk incident angle in a conventional optical pickup device. FIG. 4 is a diagram showing the relationship between the received light amount of the light receiving element and the disk incident angle in the conventional optical pickup device. FIG. 4 is a diagram showing the relationship between the received light amount of the light receiving element and the disk incident angle in the optical pickup device of this embodiment. 5 is a plan view showing an example of the structure of the wave plate in the present embodiment. FIG. 6 is a diagram showing the relationship between the amount of light received by the light receiving element and the disk incident angle in the optical pickup device of the present embodiment.
DESCRIPTION OF SYMBOLS 1 Semiconductor laser 2 Collimating lens 3 Polarizing beam splitter 4 Wave plate 5 Objective lens 6 Optical disk 7 Light receiving element

Claims (2)

A light beam from a semiconductor laser is irradiated onto an optical disk through a polarization separation element, a wave plate, and an objective lens, and reflected light from the optical disk is incident on a light receiving element through the objective lens, the wave plate, and the polarization separation element. In an optical pickup device configured to be
When synthesized the phase difference in said optical disc and the wavelength plate, set smaller concentric accordance meets the formula (Equation 1), and the phase difference goes to the outer peripheral portion from the central portion of the wavelength plate An optical pickup device characterized by that.
(Equation 1)
(1/4 + n) λ
Where λ is the wavelength of the semiconductor laser and n is 0 or an integer A light beam from a semiconductor laser is irradiated onto an optical disk through a polarization separation element, a wave plate, and an objective lens, and reflected light from the optical disk is incident on a light receiving element through the objective lens, the wave plate, and the polarization separation element. In an optical pickup device configured to be
When the phase difference Φ in the wavelength plate, that meets the following formula (Formula 2), and the phase difference is set to be smaller concentrically toward the outer peripheral portion from the center portion of the wave long plate A characteristic optical pickup device.
(Equation 2)
nλ <Φ <(1/4 + n) λ
Where λ is the wavelength of the semiconductor laser and n is 0 or an integer

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