JP2002251768A - Optical path separating element and optical pickup device using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup device which is hardly influenced by light from a light source and can obtain a detecting signal having a high S/N by efficiently separating light from the light source and fluorescence emitted from an optical recording medium. SOLUTION: In the device which condenses light being linear polarization radiated from the light source 1 and having the wavelength λ0 by an object lens 4 and produces fluorescence having the wavelength λ by irradiating the recording surface of the optical recording medium 5, the optical path of light having the wavelength λ0 reflected by the recording surface and the optical path of fluorescence having the wavelength λ generated from the recording surface are separated by the optical path separating element 3, and separated fluorescence having the wavelength λ is received by a photodetector 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical path separating element and an optical path separating method for separating light having a wavelength λ ₀ emitted from a light source from an optical path of fluorescence having a wavelength λ different from the wavelength λ _0, and uses the same. Optical pickup device and optical information processing device.

[0002]

2. Description of the Related Art There is known an optical information processing apparatus which selectively performs at least one of recording, reproducing and erasing of information on a disk-shaped optical recording medium by irradiating light from a light source. . As an optical disk, DVD-R or DVD-R
W, CD, CD-R, CD-RW, and the like, and an optical information processing apparatus corresponding to them includes an optical pickup device shown in FIG. Conventional optical pickup devices
Semiconductor laser 101 as a light source, collimator lens 102, polarization beam splitter 1 as an optical path separating element
03, objective lens 104, light collecting element 10 for detecting reflected light
6. The light detecting means 109 is provided. In the optical pickup device having such a configuration, the linearly polarized light having the wavelength λ ₀ emitted from the semiconductor laser 101 is converted into substantially parallel light by the collimator lens 102, and the polarization beam splitter 103 and a 図 示 λ phase difference plate (not shown) In the optical isolator configured by the above, the linearly polarized light is converted into the circularly polarized light. The light converted into the circularly polarized light is condensed by the objective lens 104 displaceable at least in the focusing direction by the driving of the driving unit 111, and is irradiated as a light spot on the recording surface of the optical disk 105 as an optical recording medium. .

Normally, a semiconductor laser 101 has a different emission angle in a direction perpendicular to the horizontal direction with respect to the active layer, and the collimator light passing through the collimator lens 102 has an elliptical shape. The shaping prism makes the collimator light circular to improve the coupling efficiency of the objective lens 104.

The reflected light from the recording surface of the optical disk 105 follows a path reverse to the arrival path to the optical disk, passes through the objective lens 104, and is linearly polarized light whose polarization direction is rotated by 90 ° by a λλ phase difference plate (not shown). After the conversion, the light-condensing element 106 for detection by the polarizing beam splitter 103 is used.
Reflected in the direction. The light reflected by the polarization beam splitter 103 is condensed by a condensing lens 107 and a cylindrical lens 108 constituting a condensing element 106 for detecting reflected light, and is incident on a light detecting means 109. The light detecting means 109 detects an output amount of reflected light that changes according to a difference in reflectance caused by whether or not the recording surface of the optical disc 105 has a mark. Further, in the optical pickup device, a focus error or a tracking error is detected from the output of the light detection unit 109, a servo signal is generated, and the drive unit is feedback-controlled. At least to reproduce the recorded signal. In other words, the optical pickup device corresponding to the above-described optical disc detects the amount of light of the wavelength λ ₀ reflected on the recording surface by using the reflected light of linearly polarized light emitted from the light source and the interference phenomenon, and detects a focusing error. And a tracking error signal.

[0005]

In recent years, for example, ODS
2000 support Postdeadline paper
s P22 “Introduction to FMD
As described in “technology” or the like, light having a certain wavelength, for example, a wavelength of 650 nm is emitted from a light source, and a certain wavelength, for example, 6 different from the wavelength of light from the light source.
Optical recording media that emit 80 nm fluorescence have been proposed.

When a conventional optical pickup device is used for an optical recording medium that emits such fluorescent light, since the fluorescent light is light having no coherence, it is necessary to efficiently separate an optical path from light from a light source. difficult. That is, it is difficult to efficiently separate light from an optical recording medium having a phosphor that emits fluorescent light in accordance with the irradiation light amount and irradiation light from a light source. If the optical paths of the two different wavelengths cannot be efficiently separated as described above, it is difficult to accurately detect a recording signal, a focusing error, and a tracking error.

An object of the present invention is to provide an optical path separating element and an optical path separating method which can satisfactorily separate the optical paths of light having different wavelengths even when the wavelength of the illumination light from the light source and the wavelength of the fluorescent light from the optical recording medium are different. The purpose is.

According to the present invention, the light from the light source and the fluorescent light emitted from the optical recording medium are efficiently separated, the influence of the light from the light source is small, and a detection signal having a high S / N ratio can be obtained. It is an object to provide an optical pickup device.

According to the present invention, there is provided a method of efficiently separating light from a light source and fluorescent light emitted from an optical recording medium and using a detection signal which is less affected by light from the light source and has a high S / N ratio. It is an object of the present invention to provide an optical pickup device capable of performing high-precision control.

An object of the present invention is to provide an optical information processing apparatus capable of performing information processing on an optical recording medium with high accuracy.

[0011]

In order to achieve the above object, according to the first aspect of the present invention, an optical path of light linearly polarized at a wavelength of λ ₀ and an unpolarized light of wavelength λ are used in a pickup device. And acts as a polarization beam splitter for light linearly polarized at wavelength λ ₀ and acts as a beam splitter for unpolarized light at wavelength λ longer than λ _0. Has been proposed.

According to the second aspect of the present invention, the optical path of the light linearly polarized at the wavelength λ ₀ and the optical path of the non-polarized light at the wavelength λ are separated from each other.
We have proposed an optical path separation element having a linear polarization separation function film that functions as a polarization beam splitter for light linearly polarized at ₀ and acts as a beam splitter for non-polarized light of wavelength λ. .

According to a third aspect of the present invention, in the optical path separating element according to the first or second aspect, the magnitude relationship between the wavelength λ and the wavelength λ ₀ is λ> λ ₀ . According to a fourth aspect of the present invention, in the optical path separating element according to the third aspect, the unpolarized light having the wavelength λ is fluorescent light.

According to a fifth aspect of the present invention, in the optical path separating element according to any one of the first to fourth aspects, the transmittance characteristic of the element is such that the transmittance characteristic of the element with respect to a reference wavelength λ _{0 with} respect to the S-polarized component. Is substantially zero, and is set to 50% or more at λ ₀ / λ.

According to a sixth aspect of the present invention, in the optical path separating element of the second, third or fourth aspect, the linearly polarized light separating function film has a property of transmitting 50% or more of unpolarized light at the wavelength λ. There is.

According to the seventh aspect of the present invention, an optical path of light from a first light source that emits linearly polarized light at a wavelength λ ₀ and a second light source that emits unpolarized light at a wavelength λ are separated. However, an optical path separating method using the optical path separating element according to claim 1 is proposed.

According to the eighth aspect of the present invention, an optical path of light from a first light source that emits linearly polarized light at a wavelength λ ₀ and a second light source that emits unpolarized light at a wavelength λ are separated. However, an optical path separating method using the optical path separating element according to claim 2 is proposed.

According to the ninth aspect of the present invention, the optical path of light from the first light source that emits linearly polarized light at the wavelength λ ₀ and the light from the second light source that emits unpolarized light at the wavelength λ are separated. However, an optical path separating method using the optical path separating element according to claim 3 is proposed.

According to the tenth aspect of the present invention, an optical path of light from a first light source that emits linearly polarized light at a wavelength λ ₀ and a second light source that emits unpolarized light at a wavelength λ are separated. However, an optical path separating method using the optical path separating element according to claim 4 is proposed.

According to the eleventh aspect of the present invention, an optical path of light from a first light source that emits linearly polarized light at a wavelength λ ₀ and a second light source that emits unpolarized light at a wavelength λ are separated. However, an optical path separating method using the optical path separating element according to claim 5 is proposed.

According to the twelfth aspect of the present invention, an optical path of light from a first light source that emits linearly polarized light at a wavelength λ ₀ and a second light source that emits unpolarized light at a wavelength λ are separated. However, an optical path separating method using the optical path separating element according to claim 6 is proposed.

According to the thirteenth aspect of the present invention, the light emitted from the light source is condensed by the objective lens and irradiated on the recording surface of the optical recording medium to generate fluorescence having a wavelength λ. For reproducing information, linearly polarized light of wavelength λ ₀
An optical path separating element for separating an optical path of light of wavelength λ ₀ reflected on the recording surface from a light path of fluorescence of wavelength λ generated on the recording surface, and a separated light of wavelength λ. There is proposed an optical pickup device having a light detecting means for receiving light.

According to a fourteenth aspect of the present invention, there is provided an optical pickup device using the optical path separating element according to any one of the first to sixth aspects as the optical path separating element according to the thirteenth aspect. ing.

According to a fifteenth aspect of the present invention, in the optical pickup device according to the thirteenth or fourteenth aspect, the driving means for displacing the objective lens at least in the focusing direction, and the driving of the driving means based on a signal obtained from the light detecting means. And an optical pickup device having control means for controlling the optical pickup.

According to the sixteenth aspect, the light emitted from the light source is condensed by the objective lens and irradiated on the recording surface of the optical recording medium to generate fluorescence having a wavelength λ. a performs the reproduction, the light source emitting light of wavelength lambda _0, the optical path of the emitted wavelength lambda ₀ of the light of the light path and the reflected by the recording surface wavelength lambda ₀ of the light in the linearly polarized light A first optical path separating element that transmits the optical path of the fluorescent light of wavelength λ generated on the recording surface, and separates the optical path of the light of wavelength λ ₀ and the fluorescent light of wavelength λ separated by the first optical path separating element. Second
An optical path separating element, first light detecting means for receiving the light of wavelength λ separated by the second optical path separating element, and a first light detecting means for receiving the light of wavelength λ ₀ separated by the second optical path separating element. The present invention proposes an optical pickup device comprising: a second light detecting means; a driving means for displacing the objective lens at least in a focusing direction; and a control means for controlling the driving of the driving means based on a signal obtained from the second light detecting means. ing.

According to a seventeenth aspect of the present invention, an optical pickup device using the optical path separating element according to any one of claims 1 to 6 as the second optical path separating element according to the optical pickup apparatus according to the sixteenth aspect. Has been proposed.

[0027] In the invention according to claim 18, in the optical pickup device according to claim 17, the optical path separating element according to any one of claims 1 to 6 is used as the second optical path separating element. 7. An optical path separating element according to claim 1, wherein
While using the optical path separation element according to any one of
An optical path connecting the objective lens and the first optical path division element, has proposed an optical pickup apparatus arranged 1 / 4.lamda retarder corresponding to the wavelength lambda _0.

According to the nineteenth aspect of the present invention, the first and the second
It of claims 1 to an optical path separating element using the optical path separation device according to any one of 6, the objective lens and the first 1 / 4.lamda retarder corresponding to the wavelength lambda ₀ in the optical path connecting the optical path division element 19. The optical pickup device according to claim 18, wherein the second optical path separating element is disposed by rotating the second optical path separating element by 90 degrees about the direction of the return optical axis with respect to the first optical path separating element. are doing.

According to the twentieth aspect of the present invention, the first and the second
It of claims 1 to an optical path separating element using the optical path separation device according to any one of 6, the objective lens and the first 1 / 4.lamda retarder corresponding to the wavelength lambda ₀ in the optical path connecting the optical path division element 18. The optical pickup device according to claim 17, wherein a 1 / 2λ phase difference plate corresponding to the wavelength λ ₀ is disposed in an optical path connecting the first optical path separating element and the second optical path separating element. There has been proposed an optical pickup device in which the light detecting means and the second light detecting means are arranged on the same plane.

According to a twenty-first aspect of the present invention, in the optical pickup device according to any one of the thirteenth to twentieth aspects, the driving means for displacing the objective lens at least in the focusing direction and the second light detecting means are provided. An optical pickup device having control means for controlling the driving of the driving means based on the received signal has been proposed.

According to the twenty-second aspect, at least one of recording, reproducing, and erasing of information by light is selectively performed on a disk-shaped optical recording medium that emits fluorescence when irradiated with light from a light source. A holding unit on which an optical recording medium is selectively set, a driving unit for rotating and driving the optical recording medium set on the holding unit, and irradiating the set optical recording medium with light. 22. An optical pickup device comprising: an optical pickup device that performs at least one of recording, reproduction, and erasing, and a displacement driving unit that drives the optical pickup device to be displaced in a radial direction of the optical recording medium. An optical information processing apparatus using one of them is proposed.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical path separating element and an optical path separating method according to the present invention will be described. FIG. 1 shows an optical path splitting element 3 according to the present invention and its optical path of light separated by this element. FIG. 2 shows a linearly polarized beam splitter (hereinafter referred to as “light splitting element”) applicable to the optical path splitting element 3 shown in FIG. PBS "
One representative characteristic example is shown below. FIG. 2 is an extract of a representative example of a transmittance curve of a laser line polarizing cube beam splitter described in “Laser Optics Guide V (1) Optical Components” P165 issued by Meles Griot Co., Ltd.

The light separating element 3 separates the optical path of linearly polarized light (for example, S-polarized light) at the reference wavelength λ ₀ (hereinafter referred to as “wavelength λ ₀ ”) from the optical path of unpolarized light at the wavelength λ. And acts as a polarizing beam splitter for light linearly polarized at wavelength λ ₀ , and acts as a beam splitter for unpolarized light at wavelength λ longer than wavelength λ _0. Have

The transmittance of the light separating element 3, ie, the PBS
The characteristic is, as shown in FIG. ₀Wave indicated by / λ
Long λ₀If the relative wavelength of the wavelength and the wavelength λ is 1, it is p-polarized light.
Nearly 100 percent of the light but not the s-polarized light.
At a wavelength λ for s-polarized light.₀Against
Nearly zero, wavelength λ₀/ 50% at wavelength λ
Or more.

Thus, the wavelength λ₀Is shown in FIG.
PBS having such transmittance characteristics is combined with the optical path separating element 3.
For example, by using the wavelength λ₀63 as the light
Uses a 2.8 nm HeNe gas laser (s-polarized light)
And this laser beam almost reverses as shown in FIG.
Can be fired. In this PBS, the wavelength λ ₀
Is not polarized light without polarization characteristics, for example, fluorescence
Then, the s-polarized light component of the fluorescence is almost reflected.
Can transmit only the p-polarized component of fluorescence
Becomes

As described above, PB which has been conventionally rich in mass productivity
S can be used to separate the optical path of light of wavelength λ ₀ having linearly polarized light from light of wavelength λ that does not have polarization characteristics.

As another example, the wavelength λ ₀ = 632.8.
Assuming that the p-polarized light having a wavelength of nm
Light having a wavelength shorter than 2.8 nm reflects most of the s-polarized light component, and as the wavelength becomes shorter, also reflects the p-polarized light component. Due to such characteristics, the present invention can be applied to fluorescence having a shorter wavelength.

As light of wavelength λ ₀ , He of 632.8 nm is used.
Although the Ne gas laser is exemplified, the PBS has a wavelength λ ₀
What is necessary is just to use what has the characteristic so that a high reflectance may be obtained corresponding to the light source used for, and it is not limited to the above-mentioned thing. For example, 680 nm, 650 nm, 635n
m red semiconductor laser or the like can be used. Also, depending on the phosphor, it is sufficient to select the lowest absorption band,
A semiconductor laser having a green or blue emission band can be used as a light source.

By employing such a configuration, light having a wavelength λ ₀ having linearly polarized light is reflected with high efficiency (s−
Further, an optical path separation function capable of transmitting at least 50% or more of light having a wavelength λ different from the wavelength λ ₀ having no polarization characteristics is realized.

The transmittance characteristics of PBS are as shown in FIG.
g = λ₀/ Λ is less than 1
Then, the s-polarized light is gradually transmitted, and the relative wavelength g is approximately 0.1.
Approximately 100% of s-polarized light is transmitted around 91
Characteristics. For this reason, it is longer than 632.8 nm.
Light having a wavelength λ, ie, wavelength λ and wavelength λ ₀
Λ> λ₀The light transmittance is relative wave
It is determined by the value of the length g. At this time, the wavelength λ₀Is s-polarized light
Less if unpolarized light of wavelength λ is fluorescent.
Both the p-polarized components of the fluorescence are transparent as shown in FIG.
You will have. If the fluorescence has no polarization characteristics, the average
Light power is transmitted. Therefore, regarding fluorescence
At least 50% can be transmitted.
You.

As described above, by using the PBS which has been conventionally used and has high mass productivity as the optical path separating element 3, the optical path of the light having the wavelength λ _{0 and} the light having the wavelength λ longer than that can be obtained. It becomes possible to separate.

In FIG. 2, when the value of the relative wavelength g is 0.9 or less, the transmittance of both s-polarized light and p-polarized light increases. Specifically, assuming that the light of wavelength λ ₀ is HeNe gas laser light with a wavelength of 632.8 nm, the transmittance of light having an emission wavelength of 703.2 nm or more is close to 100% without depending on the polarization direction. Can be obtained. That is, it is possible to reflect nearly 100% of linearly polarized light (s-polarized light) in the vicinity of 632.8 nm, and to transmit nearly 100% of a wavelength of 703.2 nm or more. Regarding the transmittance characteristics, s-polarized light can be transmitted even when the relative wavelength g is 0.95, so that the light transmittance can be improved. Therefore, it is possible to set the relative wavelength g to 0.95, preferably 0.9 or less, and to perform highly efficient optical path separation.

When the optical path separating element 3 has a linearly polarized light separating function film 3a as shown in FIG.
The function may have a characteristic of transmitting at least 50% of unpolarized light at the wavelength λ.

An optical path separating method using the optical path separating element 3 having the above-described characteristics will be described. For example, a semiconductor laser is used as a first light source that emits linearly polarized light at a wavelength λ ₀ , and a second light source that emits fluorescence that is unpolarized light at a wavelength λ is an optical recording medium. When the optical path separating element 3 is arranged in the radiation direction of the laser, the optical path of the emitted light of wavelength λ ₀ is changed toward the optical recording medium by the optical path separating element 3 and is irradiated on the optical recording medium, and reflected by the optical recording medium. the optical path of the light of the wavelength lambda _0, which is the optical path of the fluorescence having a wavelength lambda generated by the recording surface by receiving the light of the wavelength lambda ₀ is separated.

Next, an optical pickup device provided with the optical path separating element 3 having the above characteristics will be described. The optical pickup device shown in FIG. 3 collects light emitted from a light source 1 by an objective lens 4 and
Irradiates the recording surface 5a to generate fluorescence having a wavelength λ to reproduce at least information from the optical disk 5. The optical pickup device shown in FIG.
The optical path of the light of wavelength λ ₀ reflected at a and the optical path of the fluorescent light of wavelength λ generated on the recording surface 5 a are separated by one optical path separating element 3, and the detection is performed while obtaining the recording signal from the fluorescent light of wavelength λ. It is to generate an error signal and a servo signal.

The optical pickup device shown in FIG. 3 separates a light source 1 that emits light of wavelength λ ₀ with linearly polarized light from an optical path of light of wavelength λ ₀ reflected from the recording surface and an optical path of fluorescent light of wavelength λ. The optical path separating element 3, the light detecting means 9 for receiving the separated light of the wavelength λ, the driving means 11 for displacing the objective lens 4 at least in the focusing direction with respect to the optical disk 5, and the light detecting means 9 are obtained. A control unit 10 for controlling the driving of the driving unit 11 based on the signal is provided.

More specifically, a semiconductor laser is used as the light source 1, and a linearly polarized beam splitter is disposed as an optical path separating element 3 having a linearly polarized light separating function film 3 a via a collimator lens 2 in a radiation direction of the semiconductor laser. Have been. In the present embodiment, the wavelength λ
(See FIG. 1) that can transmit only the p-polarized component of the fluorescent light. The objective lens 4 is arranged at a position facing the optical disk 5, is provided movably in a focusing direction close to the recording surface 5 a by a driving unit 11, and follows an information track (not shown) formed on the optical disk 5. Therefore, it is configured to perform tracking drive.

In this embodiment, the light source 1 and the optical disk 5 are arranged in a positional relationship such that the radiation surface 1A of the light source 1 and the recording surface 5a form an angle of about 90 degrees. An optical system 6 for fluorescence detection is arranged in an optical path connecting the optical path separating element 3 and the light detecting means 9. The optical system 6 includes a condenser lens 7 for condensing fluorescence and a cylindrical lens 8. The light detecting means 9 detects the recording signal by detecting the light intensity of the fluorescent light. The control means 10 includes the light detection means 9
A detection error signal such as a focus error signal or a track error signal is generated from the obtained signal, a servo signal is generated in accordance with the error signal, and the driving of the driving unit 11 is controlled using the servo signal. .

In the optical pickup device having such a configuration, light having a wavelength λ ₀ of linearly polarized light (s-polarized light) emitted from the light source 1 is converted into substantially parallel light by the collimator lens 2, The light is reflected toward the optical disk 5 by the beam splitter function. The reflected light having the wavelength λ ₀ is condensed by the objective lens 104 and irradiated onto the recording surface 5 a of the optical disk 5.

From the recording surface 5a, reflected light of wavelength λ ₀
There is fluorescence of wavelength λ generated by irradiation of spot light,
The reflected light having the wavelength λ ₀ is reflected by the polarization beam splitter function of the optical path splitter 3, and the fluorescent light having the wavelength λ is transmitted through the optical path splitter 3 by the beam splitter function of the optical path splitter 3. The transmittance at this time is determined by the linearly polarized light separating function film 3.
a. The transmitted fluorescence of the wavelength λ is condensed by the condensing lens 7 and the cylindrical lens 8 and is incident on the light detecting means 9.

As described above, the light source 1 functions as a polarization beam splitter for the light of wavelength λ ₀ and the light path separating element 3 for the fluorescence of wavelength λ to function as a beam splitter. Thus, the optical path of the light reflected on the recording surface 5a and the optical path of the fluorescent light emitted on the reflective surface 5a can be satisfactorily separated, and the flare returning to the light source 1 can be reduced. Therefore, the detection signal detected by the light detection means 9 is less affected by the light from the light source 1 and has a high S / N ratio. Since the driving means 11 is controlled based on such a detection signal having a high S / N ratio,
Various operations of the objective lens 4 can be performed with high accuracy.

In this embodiment, as a means for obtaining a focusing error signal, an astigmatism method or the like employed in a conventional optical pickup device is used. Since the optical pickup device shown in FIG. 3 includes the cylindrical lens 8, astigmatism may be generated using this lens. Alternatively, the focusing error signal can be generated by various methods such as a well-known beam size method and a knife edge method. In this embodiment, since only the fluorescence is detected, it is difficult to generate a tracking error signal using the detection light. Therefore, in order to obtain a tracking error signal, using a well-known diffraction grating,
Sub-spots are generated on both sides of the main spot of wavelength λ ₀ irradiated on the recording track, and tracking is performed by the amount of reflected light obtained from this sub-spot or the amount of fluorescent light of wavelength λ emitted from the recording surface. Well-known 3
A conventional technique such as a beam method may be used.

FIG. 4 shows another embodiment of the optical pickup device according to the present invention. Note that components having the same functions as those of the optical pickup device illustrated in FIG. 3 are denoted by the same reference numerals as those used in FIG. 3, and detailed description is omitted.

The characteristics of the optical pickup device shown in FIG.
The optical path of the light of wavelength λ ₀ reflected on the recording surface 5a and the optical path of the fluorescent light of wavelength λ generated on the recording surface 5a are separated by the two optical path separating elements 3, and the recording signal is obtained from the fluorescent light of wavelength λ. , A detection error signal or a servo signal using the light having the wavelength λ ₀ .

The optical pickup device shown in FIG.
When the optical path of the emitted wavelength lambda ₀ of the light, the optical path of the wavelength lambda ₀ of the light reflected by the recording surface 5a, a first optical path for transmitting the optical path of the fluorescence having a wavelength lambda generated by the recording surface 5a The separation element 30 and the wavelength λ ₀ separated by the first optical path separation element 30
A second optical path separating element 13 for separating the optical path of the light and the fluorescent light of the wavelength λ from the optical path, and a first light detecting means 9 for receiving the light of the wavelength λ separated by the second optical path separating element 13 And the second
The second light detecting means 19 for receiving the light of the wavelength λ ₀ separated by the optical path separating element 13 and the driving of the driving means 11 of the objective lens 4 based on the signal obtained from the second light detecting means 19 And control means 100 for controlling.

More specifically, the first optical path separating element 3
For the zero and second optical path separation elements 16, linear polarization beam splitters having linear polarization separation functional films 30a and 13a are used. Linear polarized light separating function film 3 in this embodiment
As Oa and 13a, those having characteristics capable of transmitting only the p-polarized light component of the fluorescence having the wavelength λ are used (see FIG. 1).

The first optical path separating element 30 is arranged in the radiation direction of the light source 1. The second optical path separating element 16 is separated by the first optical path separating element 30 and has a wavelength λ that passes through the element.
_In the transmission direction of ₀ and the wavelength λ, the first optical path separating element 30 is arranged so that the reflection surface by the film is rotated by 90 degrees about the direction of the return optical axis with respect to the first optical path separating element 30. The optical path connecting the first optical path separating element 30 and the objective lens 4 has a wavelength λ ₀
Are arranged.

In the optical path connecting between the second optical path separating element 13 and the light detecting means 9, a condenser lens 7 for detecting fluorescence is arranged. As shown in FIG. 5, the second light detecting means 19 is arranged in the reflection direction of the wavelength λ ₀ separated by the second light path separating element 13. An optical path connecting the second optical path separating element 13 and the second light detecting means 19 includes a condensing lens 17 for condensing reflected light of wavelength λ ₀ and a cylindrical lens 1.
8 is provided.

The control means 100 controls the second light detecting means 19
A detection error signal such as a focus error signal or a track error signal is generated from the obtained signal, a servo signal is generated in accordance with the error signal, and the driving of the driving unit 11 is controlled using the servo signal. .

In the optical pickup device having such a configuration, the linearly polarized light (s-polarized light) emitted from the light source 1 and having the wavelength λ ₀ is converted into substantially parallel light by the collimator lens 2, The light is reflected toward the optical disk 5 by the beam splitter function. The reflected light of wavelength λ ₀ passes through a λλ phase difference plate, changes its polarization direction, is condensed by an objective lens 104, and is irradiated on the recording surface 5 a of the optical disk 5.

From the recording surface 5a, reflected light of wavelength λ ₀
There is fluorescence of wavelength λ generated by irradiation of spot light,
These are guided to the first optical path separating element 30 through the objective lens 104 and the λλ phase difference plate. Since the reflected light of the wavelength λ ₀ passes through the λλ phase difference plate and changes its polarization direction again, its direction is changed by 90 degrees with respect to the irradiation light. For this reason, the reflected light of the wavelength λ ₀ is not affected by the polarization beam splitter function of the first optical path splitting element 30, and the first optical path splitting action of the first optical path splitting element 30 is similar to the fluorescence of the wavelength λ. The light passes through the separation element 30. Since the transmittance at this time depends on the characteristics of the linearly polarized light separating function film 30a, the efficiency of the linearly polarized light separating function film 30a is adjusted by adjusting the ratio of reflection and transmission, so that the reflected light of wavelength λ ₀ can be sufficiently detected. It is desirable to set so that

The transmitted reflected light having the wavelength λ ₀ and the fluorescent light having the wavelength λ are incident on the second optical path separating element 30, where the wavelength λ 0
The reflected light of ₀ is reflected by the polarization beam splitter function of the second optical path separating element 13, and the fluorescent light of wavelength λ passes through the second optical path separating element 13 by the beam splitter function of the second optical path separating element 13. The transmitted fluorescence of wavelength λ is
The light is condensed by the condenser lens 7 and is incident on the first light detecting means 9. The wavelength λ ₀ reflected by the second optical path separating element 30
Is reflected by the condenser lens 17 and the cylindrical lens 1.
The light is condensed by 8 and is incident on the second light detecting means 19. Since the transmittance and reflectance of the second optical path separation element 13 depend on the characteristics of the linearly polarized light separating function film 13a,
Here, it is set so as to function as a polarizing beam splitter having a high reflectance characteristic for the reflected light of wavelength λ ₀ and to function as a beam splitter capable of obtaining a good transmittance characteristic for the fluorescence of wavelength λ. Is preferred.

As described above, the objective lens 4 and the first light
Arranging a λλ phase difference plate between the separation element 30
And the wavelength λ radiated from the light source 1₀Light and the recording surface 5a
The generated fluorescent light having the wavelength λ is converted into the first optical path separating element 30.
Can be passed. Therefore, the wavelength λ₀Reflected light
To the second polarization beam splitter 13 with improved transmission efficiency
Wavelength λ₀Increases the amount of reflected light. Also, the second
The optical path separation element has a wavelength λ ₀Polarized beams for
Functions as a splitter and emits a beam for fluorescent light of wavelength λ
Since it functions as a splitter,
Wavelength λ reflected at recording surface 5a₀Path of light and reflection surface 5a
Can separate the optical path of fluorescent light with wavelength λ
it can. Therefore, the detection detected by the first light detection means 9
The signal is less affected by the light from the light source 1 and S
/ N ratio is high. Detection with such a high S / N ratio
Since the driving means 11 is controlled based on the output signal,
Various operations of the lens 4 can be performed with high accuracy.

The second optical path separating element 13 is less affected by the light from the light source 1 and has a wavelength λ _{0 having} a large amount of light.
Reflected light is incident. Therefore, the second light detecting means 1
The detection signal detected at 9 is less affected by the light from the light source 1 and has a high S / N ratio. Since the driving unit 11 is controlled based on such a detection signal having a high S / N ratio, various operations of the objective lens 4 can be performed with high accuracy.

The optical pickup device shown in FIG. 6 is different from the optical pickup device shown in FIG. 5 in that an optical path connecting the first optical path separating element 30 and the second optical path separating element 13 has a wavelength λ _0.
The half-wave retardation plate 21 corresponding to the above is disposed.

As described above, the first optical path separation element 30 and the second
When the λλ phase difference plate 21 is disposed between the optical path separating elements 13, the polarization direction of the reflected light having the wavelength λ ₀ passing through the first optical path separating element 30 is rotated by 90 degrees. Therefore, the direction of the second optical path separating element 13 can be changed by 90 degrees as compared with the direction of the second optical path separating element 13 shown in FIG. Therefore, the second light detecting means 19 and the optical system 16 can be arranged on the same plane, and the thickness of the optical pickup device can be reduced.

In the optical pickup device shown in FIGS. 4 and 6, a linear polarization beam splitter is used as the first optical path separating element 30, and a wavelength λ ₀ having a λλ phase difference plate 20 is provided.
Although the polarization direction of has been changed, the optical pickup device,
It is not limited to such a configuration. For example, in order to separate the reflected light separated from the light (irradiation light) of wavelength λ ₀ emitted from the light source 1 and the fluorescent light of wavelength λ, a well-known dichroic mirror is used instead of the first optical path separation element 30. It can also be separated by arranging such as. 1/4
The λ retardation plate 20 may be arranged as needed.

In the optical pickup device shown in FIG. 3, since the light having the wavelength λ ₀ (reflected light) is cut by the optical path separating element 3 and only the fluorescence having the wavelength λ is detected, the tracking error signal is obtained. Although difficult, the tracking error signal can be satisfactorily obtained in the optical pickup device shown in FIGS. That is, since the fluorescent light is light having no coherence as described above, in the configuration shown in FIG. 3, the 0th-order light and the ± 1st-order light utilizing the diffraction phenomenon by the recording track grooves formed on the optical disk 5 are used. It is difficult to apply a so-called push-pull method in which a beam spot follows a recording track so that the interference pattern becomes uniform. However, in the configurations shown in FIGS. 4 and 6, the light (reflected light) having the wavelength λ ₀ is detected by the second light detecting means 19 separately from the separated fluorescence, and therefore the push-pull method is applied. be able to. Therefore, in the optical pickup device having the configuration shown in FIGS. 4 and 6, it is possible to satisfactorily generate an error signal and the like while separating the light (reflected light) having the wavelength λ ₀ and the fluorescence having the wavelength λ. Accurate driving means 1
1 can be performed.

When the optical disk 5 that emits fluorescent light has a multilayer structure, the wavelength λ from the light source 1 is applied to the target layer.
_{In order} to irradiate the _zero spot light, for example, as is well known, the objective lens 4 is servo-controlled and moved in the focusing direction so as to move close to the optical disk 5 to obtain error signals for the number of layers. Next, the focus of the objective lens 4 is focused on one of the layers, and light for reading is emitted from the light source 1 to read address information embedded or formed in advance in each layer. If the read address information indicates a desired layer, information processing on the optical disc 5 is performed by focusing the objective lens 4 on the layer from which the address information has been read. If it is not a desired address signal, an address read operation may be performed until a desired layer is detected.

Although the optical pickup device shown in FIGS. 3, 4 and 6 is of an infinite system, it may be of a finite system. In the case of a finite system, the divergent light from the light source 1 is directly irradiated on the recording surface 5a by the objective lens 4 as a light spot. In this case, since the return light flux from the recording surface 5a has a convergent light speed, the collimator lens 2 and the condenser lenses 7, 17 can be omitted from the configuration of the optical pickup device.

FIG. 7 is a diagram showing one embodiment of the optical information recording / processing apparatus of the present invention. The optical information processing apparatus includes an optical disc 150 that emits fluorescence when irradiated with light from a light source.
An optical information processing apparatus that selectively performs at least one of recording, reproducing, and erasing of information by light,
A holding unit 161 to which 0 is selectively set, and a holding unit 16
A drive motor 162 as a driving means for rotating the optical disk 150 set to 1 and a light having a wavelength unique to the medium are selected for the set optical disk 150 to perform at least one of recording, reproduction, and erasing. The optical pickup device 160 and the optical pickup device 160
The control unit 163 includes a displacement drive unit 163 that drives the displacement in the radial direction of zero. A control unit 164 in FIG. 7 is configured by a microcomputer or the like, and controls each unit of the optical information processing device. In such a configuration, by applying any one of the optical pickup devices 160 described in the above embodiment, information processing on the optical disk 150 can be performed with high accuracy.

[0072]

According to the first to twelfth aspects of the present invention,
According to the optical path separation element and the optical path separation method, even when the wavelength of the irradiation light from the light source and the wavelength of the fluorescence from the optical recording medium are different,
The optical path separating element has a function of acting as a polarization beam splitter for light linearly polarized at the wavelength λ ₀ and acting as a beam splitter for unpolarized light of the wavelength λ longer than the wavelength λ _0. Therefore, it is possible to satisfactorily separate optical paths of light having different wavelengths.

According to the thirteenth aspect of the present invention, the optical path of the light having the wavelength λ ₀ of the linearly polarized light radiated from the light source and reflected on the recording surface of the optical recording medium and generated on the recording surface by the light having the wavelength λ _0. And the optical path of the fluorescent light having the wavelength λ is separated by the optical path separating element, so that only the separated fluorescent light is detected by the light detecting means, and the detection light is hardly affected by the light from the light source. / N can be obtained.

According to the invention of claim 14, claim 1 is
In the optical pickup device according to the third aspect, since the optical path separating element according to any one of claims 1 to 6 is used as the optical path separating element, the light from the light source and the fluorescent light from the optical recording medium can be more efficiently separated. , A detection signal having a higher S / N can be obtained.

According to the invention of claim 15, claim 1 is
In the optical pickup device described in 3 or 14, the driving unit for displacing the objective lens at least in the focusing direction is controlled by the control unit using a detection signal having a high S / N ratio obtained from the light detection unit. Accurate control can be performed.

According to the sixteenth aspect of the present invention, an optical path of light having a wavelength λ ₀ of linearly polarized light radiated from a light source and reflected on a recording surface of an optical recording medium and generated on a recording surface by light having a wavelength λ _0. Since the light path of the fluorescent light having the wavelength λ is separated by the first and second optical path separating elements, the separated fluorescent light and the reflected light having the wavelength λ ₀ are hardly affected by the light from the light source. A detection signal having a high S / N can be obtained from the separation element.

According to the seventeenth aspect, in the first aspect,
In the optical pickup device according to the sixth aspect, since the optical path separating element according to any one of the first to sixth aspects is used as the second optical path separating element, the light from the light source and the fluorescent light from the optical recording medium are more efficiently emitted. It is possible to separate well and to obtain a detection signal with a higher S / N.

According to the eighteenth aspect, according to the first aspect,
7. The optical pickup device according to claim 7, wherein the optical path separating element according to any one of claims 1 to 6 is used as a first optical path separating element, and a wavelength λ is connected to an optical path connecting the objective lens and the first optical path separating element. _Since the １ ／ λ phase difference plate corresponding to ₀ is disposed, the amount of transmission of the reflected light of wavelength λ ₀ in the first optical path separation element can be increased, and detection with a higher S / N can be performed from the second optical path separation element. A signal can be obtained.

According to the invention of claim 19, claim 1
9. The optical pickup device according to 8, wherein the second optical path separation is performed.
The element is returned to the first optical path separating element and the direction of the return optical axis is changed.
By arranging the first optical path by rotating it by 90 degrees as the axis,
Wavelength λ changed by separation element ₀Efficiently reflected light of the second
Of the second optical path separation
A detection signal with a higher S / N can be obtained from the element.
You.

According to the twentieth aspect, according to the first aspect,
8. In the optical pickup device according to 8, the 1 / 2λ phase difference plate corresponding to the wavelength λ ₀ is arranged in the optical path connecting the first optical path separating element and the second optical path separating element. The polarization direction of the reflected light having the wavelength λ ₀ that has passed is rotated by 90 degrees, so that the second light detecting means 19 can be arranged on the same plane as each of the optical path separating elements, and the thickness of the optical pickup device can be reduced. be able to.

According to the twenty-first aspect, in the first aspect,
21. The optical pickup device according to any one of 3 to 20, wherein the driving means for displacing the objective lens at least in the focusing direction is controlled using a detection signal having a high S / N ratio obtained from the second light detection means. Since it is controlled by the means, accurate control can be performed.

According to the twenty-second aspect, at least one of recording, reproducing, and erasing of information by light is selectively performed on a disk-shaped optical recording medium that emits fluorescence when irradiated with light from a light source. Is provided with the optical pickup device according to any one of claims 13 to 21, so that information processing on the optical recording medium can be accurately performed.

[Brief description of the drawings]

FIG. 1 is a view for explaining one embodiment of an optical path separation element according to the present invention and the principle of separation of an optical path by this element.

FIG. 2 is a diagram illustrating an example of a transmittance characteristic of an optical path separation element.

FIG. 3 is a schematic configuration diagram showing one embodiment of an optical pickup device using an optical path separation element according to the present invention.

FIG. 4 is a schematic configuration diagram showing an embodiment of an optical pickup device using an optical path separating element according to the present invention as first and second optical path separating elements.

FIG. 5 is a diagram illustrating a configuration near a second optical path separation element and an optical path separation state viewed in the direction A in FIG. 4;

FIG. 6 is a schematic configuration diagram showing an embodiment of an optical pickup device having two phase difference plates having different characteristics by using the optical path separating element according to the present invention as first and second optical path separating elements.

FIG. 7 is a schematic configuration diagram showing an embodiment of an optical information processing device having an optical pickup device to which the present invention has been applied.

FIG. 8 is a schematic configuration diagram showing one embodiment of a conventional optical pickup device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source 2 Objective lens 3 Optical path separation element 3a, 13a, 30a Linear polarization separation functional film 5 Optical recording medium 5a Recording surface 9 Light detection means 10, 100 Control means 11 Driving means 13 Second light path separation element 19 Second light Detecting means 30 First optical path separating element 90 First light detecting means 20 1 / 4λ phase difference plate 21 1 / 2λ phase difference plate 161 Holder 162 Driving means (drive motor) 163 Displacement drive means PU Optical pickup device

Claims (22)

[Claims] [Claim 1] used in the pickup device, an optical path separating element for separating the optical path of the light of the wavelength lambda ₀ in the optical path of the light which is linearly polarized and the wavelength lambda unpolarized light which is linearly polarized at the wavelength lambda ₀ An optical path separating element having a function of acting as a polarizing beam splitter on a non-polarized light having a wavelength λ longer than the wavelength λ ₀ . 2. A used in the pickup device, an optical path separating element for separating the optical path of the light of the wavelength lambda ₀ in the optical path of the light which is linearly polarized and the wavelength lambda unpolarized light which is linearly polarized at the wavelength lambda ₀ An optical path separating element having a linearly polarized light separating function film having a function of functioning as a polarizing beam splitter and a function of acting as a beam splitter for unpolarized light having a wavelength λ. 3. The optical path separating element according to claim 1, wherein the magnitude relation between the wavelength λ and the wavelength λ ₀ is λ> λ ₀ . 4. An optical path separating element according to claim 3, wherein the unpolarized light having the wavelength λ is fluorescent light. 5. The optical path separating element according to claim 1, wherein the transmittance characteristic of the element is substantially zero for a reference wavelength λ ₀ for an S-polarized light component. And wherein λ ₀ / λ is 50% or more. 6. The optical path separating element according to claim 2, wherein the linearly polarized light separating functional film is configured to convert unpolarized light having a wavelength λ into 50.
An optical path separating element having a characteristic of transmitting a percentage or more. 7. A first device which emits linearly polarized light at a wavelength λ ₀ .
An optical path separating method for separating an optical path of light from a second light source that emits unpolarized light at a wavelength λ, and a light source according to claim 1, wherein the optical path separating element according to claim 1 is used. Separation method. 8. A first device that emits linearly polarized light at a wavelength λ ₀ .
An optical path separating method for separating an optical path of light from a second light source that emits unpolarized light at a wavelength λ, and a light source according to claim 2, wherein the optical path separating element according to claim 2 is used. Separation method. 9. A first device which emits linearly polarized light at a wavelength λ ₀ .
An optical path separating method for separating an optical path of light from a second light source that emits unpolarized light at a wavelength λ, and a light source according to claim 3, wherein the optical path separating element according to claim 3 is used. Separation method. 10. An optical path separation method for separating an optical path of light from a first light source that emits linearly polarized light at a wavelength λ ₀ and a second light source that emits unpolarized light at a wavelength λ. An optical path separation method using the optical path separation element according to claim 4. 11. An optical path separating method for separating an optical path of light from a first light source that emits linearly polarized light at a wavelength λ ₀ and a second light source that emits unpolarized light at a wavelength λ. An optical path separation method using the optical path separation element according to claim 5. 12. An optical path separating method for separating an optical path of light from a first light source that emits linearly polarized light at a wavelength λ ₀ and a second light source that emits unpolarized light at a wavelength λ. An optical path separating method using the optical path separating element according to claim 6. 13. A light beam for converging light emitted from a light source with an objective lens and irradiating the light onto a recording surface of an optical recording medium to generate fluorescence having a wavelength of λ and reproducing information from the optical recording medium. In the pickup device, a light source that emits light of wavelength λ ₀ with linearly polarized light, an optical path of light of wavelength λ ₀ reflected on the recording surface, and an optical path of fluorescent light of wavelength λ generated on the recording surface are separated. An optical pickup device comprising: an optical path separation element; and a light detection unit that receives the separated light having the wavelength λ. 14. The optical pickup device according to claim 13, wherein the optical path separating element is used as the optical path separating element.
An optical pickup device using the optical path separating element described in any one of the above. 15. The optical pickup device according to claim 13, wherein a driving unit for displacing the objective lens at least in a focusing direction, and driving of the driving unit based on a signal obtained from the light detecting unit. An optical pickup device comprising a control unit. 16. Light for condensing light emitted from a light source with an objective lens and irradiating the light onto a recording surface of an optical recording medium to generate fluorescence having a wavelength of λ, thereby reproducing information on the optical recording medium. in pickup device, a light source for emitting light having a wavelength lambda ₀ linearly polarized light, an optical path of the emitted wavelength lambda ₀ of the light, the optical path of the light of the wavelength lambda _0, which is reflected by the recording surface, with the recording surface A first optical path separating element that transmits the generated optical path of the fluorescent light of the wavelength λ, a first optical path separating element that separates the optical path of the light of the wavelength λ ₀ separated by the first optical path separating element, and the optical path of the fluorescent light of the wavelength λ. A second light path separating element, first light detecting means for receiving light of wavelength λ separated by the second light path separating element, and receiving light of wavelength λ ₀ separated by the second light path separating element An optical pickup device comprising: a second light detection unit. 17. The optical pickup device according to claim 16, wherein the second optical path separating element is used as the second optical path separating element.
An optical pickup device using the optical path separation element described in any one of the above. 18. The optical pickup device according to claim 17, wherein the first optical path separating element is used as the first optical path separating element.
The objective lens and the first
1 corresponding to the wavelength λ ₀
An optical pickup device comprising a / 4λ retardation plate. 19. The optical pickup device according to claim 18, wherein the second optical path separating element is arranged so as to be rotated by 90 degrees about the direction of the return optical axis with respect to the first optical path separating element. Optical pickup device. 20. A optical pickup apparatus of claim 18, the optical path connecting the first optical path division element the second optical path division element, by arranging the 1/2 [lambda] retarder corresponding to the wavelength lambda _0,
An optical pickup device wherein the first light detecting means and the second light detecting means are arranged on the same plane. 21. The optical pickup device according to claim 13, wherein a driving unit for displacing the objective lens at least in a focusing direction and a signal obtained from the second light detection unit. An optical pickup device, comprising: control means for controlling the driving of the driving means. 22. An optical information processing apparatus for selectively performing at least one of recording, reproducing, and erasing of information by light with respect to a disk-shaped optical recording medium which emits fluorescence when irradiated with light from a light source. A holding unit in which the optical recording medium is selectively set; a driving unit for rotating the optical recording medium set in the holding unit; and irradiating light to the set optical recording medium. 22. An optical pickup device for performing at least one of recording, reproduction, and erasing by using an optical pickup device, and a displacement driving means for driving the optical pickup device to be displaced in a radial direction of the optical recording medium. An optical information processing apparatus characterized by using any one of the above.