JPH09245368A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain compatibility in reproduction between optical recording media with different distances from a surface of a reproducing light incident side to a recording surface such as a CD and a DVD(digital video disk) by a simple structure, to reduce a cost of a device and to miniaturize it. SOLUTION: This device is constituted of an aperture forming element 3 disposed on a forward optical path between a light source 1 and a reflection optical recording medium 6 and capable of forming a transmission area 4a transmitting through reproducing light and a non-transmission area 4b with relatively low transmissivity for the reproducing light by containing dye changing an absorption spectrum by e.g. a photon mode reaction, and the formation of the transmission area 4a and the non-transmission area 4b of the aperture forming element 3 are controlled by irradiating the aperture forming element 3 with the light from the light source 7 different from the reproducing light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of an optical pickup device for reproducing an optical recording medium.

[0002]

2. Description of the Related Art A digital video disc (DVD) capable of recording a moving image such as a movie on a compact disc having a diameter of 120 mm for two hours or more has been actively developed. Conventional compact discs (CDs) use transparent substrates such as polycarbonate with a thickness of 1.2 mm, but DVDs have a structure in which transparent substrates such as polycarbonate with a thickness of 0.6 mm are bonded together. Has been done.

If such an optical pickup device for DVD is also used for a conventional optical pickup device for CD, the thickness of the substrate, that is, the distance from the substrate surface to the recording layer is different, so that the influence of aberration is exerted. It becomes large, and it becomes difficult to obtain a good light spot for both substrates. For this reason, in order to reproduce both the conventional CD and the DVD having a thin substrate with one pickup device, a special device is required for the pickup device.

As a method of solving such a problem, the pickup itself has two objective lenses corresponding to a thick substrate and a thin substrate, that is, a thick substrate has a low NA (numerical aperture) lens and a thin substrate. High NA for substrate
A method has been proposed in which (numerical aperture) lenses are provided and these lenses are mechanically switched according to the substrate.

Also proposed is a system in which only a single objective lens corresponding to a thin substrate is provided, and when reproducing a disc on a thick substrate, an aperture is inserted in the optical path to reduce the substantial NA. According to such a system, a thin substrate DVD having a thickness of 0.6 mm and a thickness of 1.2 mm
It becomes possible to play back together with the conventional CD of mm.
Playback compatibility can be obtained.

[0006]

However, in the method of switching the lenses, it is necessary to provide two objective lenses inside the pickup, and a mechanism for switching the lenses is required, which makes it difficult to reduce the size and cost. There was a problem. Further, the method of inserting the aperture into the optical path can have a simpler structure than the method of switching the lens described above, but again, a mechanical mechanism for inserting the aperture into the optical path is required, and the cost is low. There is a problem that it is difficult to reduce the size and size.

An object of the present invention is to achieve compatibility in reproduction between optical recording media such as CD and DVD having different distances from the surface on the incident side of reproduction light to the recording surface with a simpler structure, An object of the present invention is to provide an optical pickup device that can realize cost reduction and size reduction.

[0008]

SUMMARY OF THE INVENTION An optical pickup device of the present invention is an optical pickup for irradiating a reflective optical recording medium with reproduction light and detecting the reflected light to reproduce information recorded on the medium. The device is a light source that emits reproduction light,
It is provided in the forward light path between the light source and the reflective recording medium. For example, a transmissive region that transmits the reproduction light by containing a pigment whose absorption spectrum changes due to a photon mode reaction and a transmittance for the reproduction light is in the transmission region. Aperture forming means capable of forming a relatively low opaque region and a reproduction light source for causing the aperture forming means to change the absorption spectrum of the dye are irradiated with light from a different light source. And means for controlling the formation of the transparent area or the non-transparent area of the aperture forming means.

In the present invention, it is preferable that a transmissive region is formed inside the reproduction light incident region of the aperture forming means, preferably at a substantially central portion thereof, and a non-transmissive region is formed at a peripheral portion thereof.

According to the invention, the control means irradiates the aperture forming means with light from a light source different from the reproduction light source to control the formation of the transmissive region or the non-transmissive region of the aperture forming means. This makes it possible, like CDs and DVDs,
It is possible to achieve compatibility in reproduction between different optical recording media. That is, when reproducing a disk with a thick substrate such as a CD, an opaque area is formed in the peripheral portion of the reproduction light incident area of the aperture forming means, thereby lowering the substantial NA (numerical aperture). You can DVD
When reproducing a thin substrate such as the one described above, the opaque region is not formed in the reproduction light incident region of the aperture forming means, or the area of the opaque region is made relatively small so that the disc of the thick substrate is The substantial NA (numerical aperture) can be increased more than that at the time of reproduction.

According to the present invention, by irradiating the aperture forming means with the light from the light source different from the reproduction light source, the substantial NA can be controlled.
It is possible to achieve compatibility in reproduction between different optical recording media such as DVD and DVD. Therefore, compatibility in reproduction can be obtained with a simpler structure than before, and cost reduction and miniaturization can be realized.

Further, according to the present invention, it is possible to freely control the formation position and the size of the transparent region and the non-transparent region formed in the aperture forming means. Therefore,
Apertures of various diameters can be formed, and the optical discs of various thicknesses can be used without being limited to CDs and DVDs.

In the first aspect of the present invention, the peripheral portion of the reproducing light incident area of the aperture forming means is irradiated with colored light from the control means to form an opaque area in the peripheral portion. Is formed. That is,
According to the first aspect, the dye contained in the aperture forming means irradiates the colored light as the light from another light source to cause a coloring reaction in the photon mode, for example.
This is a dye that can form an opaque region. Further, the control means irradiates the colored light to the peripheral portion of the reproduction light incident area of the aperture forming means, thereby forming an opaque area in the peripheral portion of the reproduction light incident area of the aperture forming means.

According to the first aspect, by forming the opaque region in the peripheral portion of the aperture forming means in the reproduction light incident region in this manner, a substantial aperture is formed and a substantial NA is formed. It can be lowered to play thicker substrate discs such as CDs. When reproducing a disc having a thin substrate such as a DVD, the irradiation of the colored light from the control means is not performed or the intensity thereof is reduced. As a result, the non-transparent region in the peripheral portion in the reproduction light incident region of the aperture forming means disappears or the area thereof decreases, and the substantial NA is increased.

In the first aspect, the following method may be mentioned as a method of irradiating the peripheral portion in the reproduction light incident area of the aperture forming means with colored light. A first method is a method in which the control means has a colored light source that emits colored light from an annular light emitting surface. In such a method, by irradiating the colored light emitted from the colored light source as the separate light source into the reproduction light incident area of the aperture forming means, the peripheral light can be irradiated with the colored light. It is possible to form an opaque region.

A second method is a method in which the control means has a colored light source as the other light source for emitting colored light and a shield material provided in the optical path between the colored light source and the aperture forming means. is there. The shield material shields the colored light so that the colored light emitted from the colored light source is applied to the peripheral portion in the reproduction light incident area of the aperture forming means. Therefore, by irradiating the colored light from such control means into the reproduction light incident area of the aperture forming means, it is possible to irradiate the colored light to the peripheral portion and form the opaque area in the peripheral portion. be able to. The shield material is preferably provided at a place where reproduction light does not pass.

In the first aspect, the area of the non-transmissive area in the reproduction light incident area of the aperture forming means is changed by changing the position of the light source in the control means or the position or shielding area of the shield material. It may be controllable. By making the area of the opaque region variably controllable in this way, the substantial NA can be variably controlled.

In the second aspect of the present invention, the entire reproduction light incident region of the aperture forming means is irradiated with colored light, the whole is colored, and then the reproducing light is irradiated to the aperture forming means. The light intensity distribution is used to erase the color in the reproduction light incident region, preferably in the central portion, to form a transmission region. That is, since the intensity of the reproducing light beam in the central portion is usually higher than that in the peripheral portion, the decolorizing reaction occurs preferentially in the area irradiated with the reproducing light, preferably in the central portion to form a transmissive area. It

Therefore, in the second aspect, a coloring reaction due to, for example, a photon mode reaction is caused by irradiating coloring light as light from a reproduction light source and a different light source as the dye contained in the aperture forming means. A dye is used that forms a non-transmissive region and irradiates reproducing light to cause a decoloring reaction in, for example, a photon mode, thereby forming a transparent region.

In the second aspect, the control means irradiates the entire inside of the reproduction light incident area of the aperture forming means with the colored light, as described above. As a result, the entire reproduction light incident region of the aperture forming means is colored, but when the reproduction light is irradiated onto this, a decoloring reaction occurs in the reproduction light irradiation region, preferably in the center thereof, and the transmitted light is transmitted. A region is formed. Therefore, a coloring reaction due to the colored light occurs in the peripheral portion in the reproduction light incident area of the aperture forming means to form an opaque area, and an erasing reaction due to the reproduction light occurs in the inside thereof to form a transmissive area. As a result, the substantial NA is lowered, and an optical disc having a thick substrate such as a CD can be reproduced.

In the second aspect, when reproducing an optical disc having a thin substrate such as a DVD, the irradiation of the colored light to the reproduction light incident area of the aperture forming means is stopped or the intensity of the colored light is reduced. . As a result, the non-transmissive region due to the colored light disappears or the area thereof is reduced, and a transmissive region having a wider area is formed, so that the substantial NA can be increased and an optical disc such as a DVD can be reproduced. Will be able to.

In the above first and second aspects,
The dye contained in the aperture forming means can be used in a wide range as long as it is a dye that causes a coloring reaction or an erasing reaction as described above, but in order not to be affected by the ambient temperature, It is preferable to use a photochromic dye that hardly causes coloring and decoloring due to thermal reaction. Examples of such photochromic dyes include diarylethene-based photochromic dyes.

In the third aspect of the present invention, as the dye contained in the aperture forming means, a dye exhibiting a colored state with respect to reproduction light at room temperature is used as the dye contained in the aperture forming means. Part of the reproduction light incident area, preferably the central portion, is irradiated with the decolorized light, or the central portion is irradiated with the decolorized light having a high light intensity. As a result, a transmission region is formed inside the reproduction light incident region of the aperture forming means, preferably in the center. Therefore, as the dye contained in the aperture forming means, a dye that exhibits a colored state at room temperature as described above and that irradiates with decolorizing light, for example, causes a decoloring reaction in the photon mode to form a transmissive region is used. .

According to the third aspect, it is possible to form the aperture having the transparent region formed inside the non-transparent region. Therefore, the substantial NA can be reduced, and C
It is possible to reproduce an optical disc having a thick substrate such as D.

In the third aspect, when reproducing an optical disk having a thin substrate such as a DVD, the decoloring light is applied to the entire reproduction light incident area of the aperture forming means or the light intensity of the central portion is high. The light intensity of the entire decolorized light is increased, and the area of the transmission region is increased. As a result, the substantial NA can be increased, and an optical disc having a thin substrate such as a DVD can be reproduced.

In the third aspect, if the erasing area of the erasing light or the light intensity of the erasing light can be variably controlled, the formation area of the aperture formed by the aperture forming means can be variably controlled. , Various substantial NA
Can be realized.

The aperture forming means in the present invention is formed by containing the above dye, and can be formed, for example, from a thin film or a molded body containing the above dye. Such a thin film or molded body can be formed from a polymer containing a dye. Further, in the case of a thin film, a dye may be vapor-deposited to form a thin film. Further, such a thin film may be provided on a transparent support and held by a holder. Further, the aperture forming means may be incorporated in the optical element in the optical path of the reproduction light between the light source and the medium. That is, a thin film serving as an aperture forming means may be provided on the surface of such an optical element. When the optical element is made of plastic or the like, the dye may be contained in the optical element itself to give the optical element a function of aperture forming means.

An optical pickup device according to still another aspect of the present invention is an optical pickup device that irradiates an optical recording medium with reproduction light to reproduce information, and includes a first light source for emitting reproduction light and a first light source. And a shielding member that is provided in the forward light path between the light source and the optical recording medium and that can change the size of the light transmitting region that transmits the reproduction light, and the size of the light transmitting region of the shielding member. And a second light source that emits control light for controlling.

As the shielding member of the optical pickup device in this aspect, for example, the above-mentioned aperture forming means can be used. Further, the first light source corresponds to the above-mentioned reproduction light source, and as the second light source, for example, a light source different from the above reproduction light source can be used. In this aspect, the optical recording medium is not limited to the reflection type optical recording medium, and for example, the reproducing light is emitted from one side of the optical recording medium and the reproducing light passing through the medium is detected on the other side. It is also applicable to such a transmission type optical recording medium.

As the light emitted from the light source other than the reproduction light source and the second light source in the present invention, light having a wavelength different from that of the reproduction light emitted from the reproduction light source is generally used. The invention is not limited to this,
Light having substantially the same wavelength as the reproduction light emitted from the reproduction light source may be used as the light from the separate light source or the second light source. The light having the same wavelength as that of the reproduction light emits the light having the same wavelength as the reproduction light from another light source or the second light source when the intensity of the light from the reproduction light source is low. By increasing the height, it can be used when controlling the aperture forming means.

In the present invention, the "non-transmissive region" means not only a region which does not substantially transmit the reproduction light but also a low transmission region which reduces the intensity of the reproduction light to the extent that the reproduction light cannot be substantially contributed to the reproduction. It also includes. The transmittance of the non-transmissive region for reproducing light is not particularly limited,
The transmittance may be such that the NA can be controlled substantially.
Generally, a transmittance of 10% or less is preferable, and a transmittance of 5% or less is more preferable.

[0032]

1 is a block diagram showing an optical pickup device according to an embodiment of the first aspect of the present invention. Referring to FIG. 1, a collimator lens 2 for shaping the reproduction light is provided on the light emission side of the light source 1 for emitting the reproduction light. An objective lens 5 is provided on the light incident side of an optical disk 6 which is an object for reproducing information by irradiation of reproducing light. Between the collimator lens 2 and the objective lens 5, an aperture forming element 3 which is an aperture forming means in the present invention is provided. Therefore, the aperture forming element 3 is provided in the forward light path between the light source 1 and the optical disk 6.

Between the aperture forming element 3 and the collimating lens 2, there is provided a dichroic mirror 8 tilted at about 45 ° with respect to the traveling direction of the reproduction light. A colored light source 7 is provided for reflecting the dichroic mirror 8 and irradiating the aperture forming element 3 with colored light. The colored light source 7 has a ring-shaped, that is, a donut-shaped light emitting surface, and emits colored light from the donut-shaped light emitting surface to illuminate the aperture forming element 3 with the donut-shaped colored light. Therefore, only the peripheral portion of the aperture forming element is illuminated with the colored light. As the colored light source 7, for example, a high-luminance blue light emitting diode arranged in a donut shape can be used.

The aperture-forming element 3 contains a photochromic dye, and when the photochromic dye is irradiated with the colored light from the colored light source 7, the photochromic dye causes a coloring reaction in the photon mode and becomes a colored state. Is used. Further, in the present embodiment, a dye that causes a decoloring reaction in the photon mode when irradiated with reproduction light emitted from the light source 1 is used as the dye.

FIG. 2 is a plan view showing a coloring state in the reproduction light incident area 4 of the aperture forming element. FIG.
(A) shows a state when the reproduction light incident region 4 of the aperture forming element is irradiated with donut-shaped colored light. In the peripheral portion of the reproduction light incident region 4 where the colored light is irradiated, a coloring reaction due to the photon mode occurs and an opaque region 4b is formed. Further, in the central part where the colored light is not irradiated, a transmissive region 4a having a high transmittance of the reproduction light is formed.

The opaque region 4b shown in FIG. 2 (a) can change the area of the region by changing the irradiation region of the colored light or the light intensity of the colored light. Therefore, it is possible to change the diameter of the transmissive region 4a serving as the aperture of the aperture, and it is possible to change the substantial NA. Further, in the present embodiment, since the dye that causes the decoloring reaction by irradiation with the reproduction light is used as the dye contained in the aperture forming element, the diameter of the transmission region 4a can be changed by changing the beam intensity of the reproduction light. Can be changed. That is, in general, the beam light emitted from a semiconductor laser or the like has a light intensity distribution in which the intensity is higher in the central portion, so that the decolorization reaction is likely to occur in the central portion of the reproduction light beam and the overall beam intensity is increased. As a result, the region where the beam intensity is high is expanded, and the diameter of the transmission region 4a can be increased.

Referring to FIG. 1 again, when reproducing an optical disk having a thicker substrate such as a CD, as shown in FIG. 1, the opaque region 4b is formed around the aperture forming element 3.
And the reproducing light is irradiated only through the transmissive region 4a, the substantial NA can be reduced.

In the apparatus shown in FIG. 1, when reproducing an optical disc having a thin substrate such as a DVD, the irradiation of the colored light from the colored light source 7 is stopped or the colored light beam from the colored light source 7 is emitted. Reduce strength. This allows
The non-transmissive region 4b disappears or the area thereof decreases, and the diameter of the transmissive region 4a increases. In the present embodiment, since the dye that causes the decoloring reaction by the reproduction light is used, the disappearance or the area reduction of the non-transmissive region 4b can be performed more reliably.

FIG. 2B is a plan view showing a state in which the opaque area 4b has disappeared. As shown in FIG.
The non-transmissive region 4b disappears, and the entire reproduction light incident region 4 becomes the transmissive region 4a. Therefore, the substantial NA can be increased and an optical disc having a thin substrate such as a DVD can be reproduced.

FIG. 2C is a plan view showing a state in which the area of the opaque region 4b is reduced. Also in this case, the substantial NA can be similarly increased. FIG. 3 is a block diagram showing the apparatus of the embodiment shown in FIG. 1 in more detail. As shown in FIG. 3, the objective lens 5 and the aperture forming element 3
A beam splitter 9 having a half mirror is provided between them. A detector 10 is provided to detect the reflected light separated by the beam splitter 9. The detector 10 detects a reproduction signal included in the reflected light and also detects a focus error signal and a tracking error signal. The focus servo adopts the astigmatism method and the tracking servo adopts the differential push-pull method.

With reference to FIG. 3, when reproducing a CD or the like, a colored light intensity control signal can be applied to the colored light source 7 to form a sufficient opaque region 4b in the aperture forming element 3. Emit intense colored light. This colored light is reflected by the dichroic mirror 8 and applied to the aperture forming element 3. The peripheral portion of the aperture forming element 3 is irradiated with colored light to form an opaque region 4b. Along with this, a transmissive region 4a is formed in the inner central portion.
The reproduction light emitted from the reproduction light source 1 is shaped by passing through the collimator lens 2 and given to the aperture forming element 3. The reproduction light passes through the transmission region 4a in the central portion of the aperture forming element 3, the beam diameter thereof is reduced, and the objective lens 5
Given to. Since the beam diameter is reduced and is incident on the objective lens 5, the substantial NA is lowered, and it is possible to deal with CD and the like. The reproduction light reflected from the optical disk 6 passes through the objective lens 5 again, is reflected by the half mirror of the beam splitter 9, and is sent to the detector 10. The detector 10 detects the focus error signal and the tracking error signal together with the reproduction signal.

When reproducing a DVD or the like using the apparatus of FIG. 3, a colored light intensity control signal is given to the colored light source 7.
The irradiation of the colored light is stopped or the light intensity of the colored light is reduced so that the opaque region 4b of the aperture forming element 3 is not formed or the area thereof is reduced. Thereby, the transmissive region 4a of the aperture forming element 3 is formed.
The reproduction light from the reproduction light source 1 is given to the objective lens 5 with a larger beam diameter. Therefore, the substantial NA is increased. Therefore, the recording layer of an optical disc such as a DVD can be reproduced. The reflected light from the disk 6 is given to the detector 10 as described above.

FIG. 4 (a) shows the molecular structure of the dye contained in the aperture forming element 3 in the apparatus of the embodiment shown in FIGS. Further, FIG. 4B shows an absorption spectrum of this dye. As shown in FIG. 4B, it can be seen that this photochromic dye causes a photon-mode coloring reaction when exposed to blue light and a photon-mode decolorization reaction when exposed to red light. Therefore, blue light can be used as colored light and red light can be used as decolorized light. In the apparatus of the embodiment shown in FIGS. 1 and 3, red light is used as the reproduction light because the decolorization reaction is caused by the reproduction light. Specifically, laser light from a semiconductor laser having a wavelength of 680 nm is used.

In the embodiment shown in FIGS. 1 and 3, the aperture forming element has a diarylethene-based photochromic dye as shown in FIG.
The dispersion was dispersed in the order of concentration of 0 ⁻³ mol / l, put in a predetermined mold, and the solvent was evaporated to form an optical element. The optical density of the device is 0.2 to 2.
Various things up to 0 were produced. The optical density at the time of complete coloring is defined by the concentration of colored molecules (mol / l), the thickness of the element (cm), and the molecular extinction coefficient (l / mol · cm) of the dye at the reproduction light wavelength. is there. Therefore, it can be adjusted by changing the concentration of the coloring molecules of the photochromic dye or by changing the thickness of the optical element.

The relationship between the radiation power of the colored light and the spot diameter was determined by using an aperture forming element having an optical density of 0.8 when colored. FIG. 5 is a diagram showing the relationship between the colored light power and the spot diameter. With a device as shown in FIG.
The reproducing light power was kept constant at 1 mW, the coloring light power was gradually increased from 1 mW, and the spot diameter of the reproducing light beam was measured. As shown in FIG. 5, when the reproducing light power is about 1 mW or less, the spot diameter is 0.8 μm used in a DVD or the like, and when the coloring light power is about 4 mW, it is used for a conventional CD. It can be seen that the spot diameter is 1.6 μm. As described above, by changing the power of the colored light, the substantial NA can be changed and the spot diameter can be changed. In the present embodiment, since the dye that causes the decoloring reaction by the reproduction light is used as the dye of the aperture forming element, the coloring light power is kept constant and the reproduction light power is changed to change the substantial NA. It is also possible.

Next, using a device as shown in FIG.
A D-type play-only disc was played. As the DVD type disc, a disc made of polycarbonate having a substrate thickness of 0.6 mm, the shortest pit (3T signal) = 0.42 μm, and a track pitch of 0.8 μm was used. When the colored light power was 0 mW, that is, the colored light was not irradiated, and the entire reproduction light incident area of the aperture forming element was used as the transmissive area to reproduce the DVD disk, good output was obtained.

Next, the conventional CD disc was reproduced. C
As the D disc, a CD disc made of polycarbonate having a substrate thickness of 1.2 mm, a shortest pitch (3T signal) = 0.83 μm, and a track pitch of 1.6 μm was used. When an aperture forming element having an optical density of 0.8 at the time of coloring was used and the coloring light power was set to 4 mW and the reproduction light power was set to 1 mW to reproduce the EFM signal of the CD disc, a good output was obtained.

Next, as an aperture forming element, an element in which the optical density at the time of coloring was changed was prepared, and the relationship between the optical density of the aperture forming element and the quality of the reproduced signal was examined. The optical density of the aperture forming element was changed by changing the thickness of the element between 1 mm and 3 mm. The colored light power was set to 4 mW and the reproduction power was set to 1 mW, the above CD disk was reproduced, and the jitter value of the output signal was measured. FIG. 6 is a diagram showing the relationship between the optical density of the aperture forming element and the jitter value. As is clear from FIG. 6, when the optical density is 0.8 or more, a good jitter value can be obtained.

FIG. 7 is a configuration diagram showing an optical pickup device of another embodiment according to the first aspect of the present invention. In the present embodiment, the colored light from the colored light source 7 is provided so as to be reflected by the half mirror of the beam splitter 9 and be applied to the aperture forming element 3. The other configurations are similar to those of the embodiment shown in FIG. 3, and thus the description thereof will be omitted. As in the present embodiment, the half mirror of the beam splitter 9 reflects the colored light from the four-illumination light source 7 and irradiates the aperture forming element 3 with the colored light, so that the dichroic light is emitted as compared with the embodiment shown in FIG. No need for mirrors. Therefore, the configuration can be further simplified.

FIG. 8 is a configuration diagram showing an optical pickup device of still another embodiment according to the first aspect of the present invention. In the present embodiment, the shield material 11 is provided on the light emitting side of the colored light source 7. Such a shield material 11
Due to the presence of the colored light, the colored light from the colored light source 7 has an annular shape, that is, a donut shape, and is applied to the aperture forming element 3. In this embodiment, a collimator lens is not provided on the light emitting side of the reproduction light source 1, and the objective lens 5 is directly irradiated with light through the diffraction grating 12 and the aperture forming element 3. The diffraction grating 12 is an optical element for dividing the reproduction light into three beams to form a sub-beam for tracking servo, and is also provided in the optical pickup device of the above-mentioned embodiment, but in each drawing, , Which are omitted in the figure.

The present embodiment is not provided with the colored light source having the annular light emitting surface as in each of the above embodiments, but is provided with a control means provided with a shield material on the light emitting side of the colored light source. In the present embodiment, the irradiation area of the colored light can be changed by changing the shielding area of the shield material 11 or by changing the distance from the colored light source 7. Thereby, the area of the opaque region 4b of the aperture forming element 3 can be changed and the diameter of the aperture can be changed. When reproducing a DVD or the like, in addition to the method of stopping the coloring from the colored light source 7 or reducing the intensity of the colored light, the shielding material 11 prevents the colored light from reaching the aperture forming element 3. It is also possible to adopt a method of shielding the film.

FIG. 9 is a block diagram showing an optical pickup device of one embodiment according to the second aspect of the present invention. In the present embodiment, a colored light source 20 is provided which can illuminate the entire reproduction light incident area of the aperture forming element 3 with colored light. As the dye contained in the aperture forming element 3, a dye that is colored by the colored light from the colored light source 20 and is decolorized by the irradiation of the reproduction light from the light source 1 is used. Specifically, for example, a dye having the structure shown in FIG. 4A can be used.

The colored light from the colored light source 20 is reflected by the dichroic mirror 8 and is applied to the aperture forming element 3. In the aperture forming element 3, since the entire reproduction light incident area is irradiated with the colored light, the entire area is colored. In this state, the reproduction light from the light source 1 is applied to the aperture forming element 3. Since the reproduction light beam has a light intensity distribution with a high intensity in the central portion, when the reproduction light is irradiated onto the aperture forming element in such a colored state, the central portion with a high light intensity is preferentially erased. A reaction occurs and a transparent region 4a is formed in the central part. The reproduction light passes through this transmission area 4a,
Since the optical disk 6 is irradiated through the objective lens 5,
Substantial NA is lowered and a disc such as a CD can be reproduced.

When reproducing a disc such as a DVD,
By stopping the irradiation of the colored light from the colored light source 20 or by reducing the intensity of the colored light, the area of the transmission region 4a can be increased and the diameter of the aperture can be increased. As a result, the effective NA increases and DV
An optical disc such as D can be reproduced.

Also, by increasing the beam intensity of the reproduction light, it is possible to increase the area of the transmission region 4a and increase the diameter of the aperture. When the opaque region 4b in the aperture forming element 3 does not completely disappear in this way, as shown in FIG. 2C, the permeable region 4a is formed with the opaque region 4b having a narrow width formed in the periphery. Area becomes larger and the diameter of the aperture becomes larger.

FIG. 10 is a block diagram showing an optical pickup device of one embodiment according to the third aspect of the present invention. FIG.
0, in this embodiment, the aperture forming element 3
An inverse photochromic dye is used as a dye contained in the above, and a dye system that is colored at room temperature and causes an erasing reaction by irradiation with erasing light from the erasing light source 21 is used. Specifically, for example, spiroselenazolinobenzopyran dispersed in polymethacrylic acid can be used.

The erasing light source 21 is provided at a position where the emitted erasing light is reflected by the dichroic mirror 8 and is applied to the aperture forming element 3. As the erasing light source 21, a light source having an intensity distribution such that the central portion of the erasing light beam has a high light intensity is used. Therefore, since the light intensity of the decolorized light is high in the central portion of the aperture forming element 3 irradiated with the decolorized light emitted from the decolorized light source 21,
The transmissive region 4a is formed, and since the light intensity is weak around the transmissive region 4a, it remains colored and becomes the non-transmissive region 4b. Therefore, the reproduction light emitted from the light source 1 passes through the transmissive region 4a, its beam diameter is reduced, passes through the objective lens 5, and the substantial NA is lowered, so that an optical disc such as a CD can be reproduced.

When the apparatus of this embodiment is used to reproduce a disc such as a DVD, the total light intensity of the decolorized light emitted from the decolorized light source 21 is increased, and the area of high light intensity is increased. This makes it possible to increase the area of the transmissive area 4a and increase the diameter of the aperture. Therefore, the beam diameter of the reproduction light can be increased, the substantial NA can be increased, and the optical disk such as the DVD can be reproduced. As described above, according to the present invention, an optical pickup device capable of reproducing different optical disks such as a DVD and a CD can be provided.

In each of the above embodiments, the aperture forming element of the present invention is provided on the light source side with respect to the objective lens, but the present invention is not limited to this, and is provided on the medium side with respect to the objective lens. It may be provided, or may be provided immediately in front of the light source. Further, the aperture forming means may be provided integrally with optical elements such as an objective lens, a collimator lens, and a beam splitter. Furthermore, when the optical element is formed of plastic or the like, the dye of the aperture forming means of the present invention may be contained to give the optical element itself a function as an aperture forming element.

[0060]

According to the present invention, it is possible to achieve compatibility in reproduction between media having different substrate thicknesses with a simpler structure. Therefore, an optical pickup device having reproduction compatibility can be manufactured at low cost and in a smaller size.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an optical pickup device of an embodiment according to a first aspect of the present invention.

FIG. 2 is a plan view showing a colored state and a decolored state of the aperture forming element according to the present invention.

FIG. 3 is a configuration diagram showing the embodiment shown in FIG. 1 in more detail.

FIG. 4 is a diagram showing a chemical structural formula (a) and an absorption spectrum (b) of a dye contained in an aperture forming element according to an embodiment of the present invention.

FIG. 5 is a diagram showing a relationship between a coloring light power and a spot diameter of reproduction light according to an embodiment of the present invention.

FIG. 6 is a diagram showing the relationship between the optical density when the aperture forming element is colored and the jitter value of the reproduced signal in the embodiment of the present invention.

FIG. 7 is a configuration diagram showing an optical pickup device of another embodiment according to the first aspect of the present invention.

FIG. 8 is a configuration diagram showing an optical pickup device of still another embodiment according to the first aspect of the present invention.

FIG. 9 is a configuration diagram showing an optical pickup device of an embodiment according to a second aspect of the present invention.

FIG. 10 is a configuration diagram showing an optical pickup device of an embodiment according to a third aspect of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Reproducing light source 2 ... Collimating lens 3 ... Aperture forming element 4 ... Reproducing light incident area of the aperture forming element 4a ... Transmission area 4b ... Non-transmission area 5 ... Objective lens 6 ... Optical disk 7 ... Colored light source 8 ... Dichroic mirror 9 ... Beam splitter 10 ... Photodetector 11 ... Shield material 12 ... Diffraction grating 20 ... Colored light source 21 ... Decolorized light source

Claims (15)

[Claims] 1. An optical pickup device for irradiating a reflective optical recording medium with reproducing light, detecting the reflected light, and reproducing information recorded on the medium, wherein the light source emits the reproducing light. And a transmittance region for transmitting the reproduction light and a transmittance for the reproduction light, which is provided in a forward light path between the light source and the reflective optical recording medium and contains a dye whose absorption spectrum changes. Aperture forming means capable of forming an opaque region relatively lower than a transmissive region, and the reproduction light source different from the reproducing light source for causing the aperture forming means to change the absorption spectrum of the dye An optical pickup device comprising means for controlling the formation of the transmissive region or the non-transmissive region of the aperture forming means by irradiating light from a light source. 2. The optical pickup device according to claim 1, wherein the dye contained in the aperture forming means is a dye whose absorption spectrum is changed by a photon mode reaction. 3. The control means controls the transparent area to be formed in a reproduction light incident area of the aperture forming means, and the non-transparent area to be formed in a peripheral portion of the transparent area of the aperture forming means. The optical pickup device according to claim 1 or 2. 4. The dye contained in the aperture forming means is a dye that forms a non-transparent region by causing a coloring reaction by irradiating colored light as light from the reproduction light source and a light source different from the reproduction light source. The control means irradiates the colored light to the peripheral portion of the reproduction light incident area of the aperture forming means, whereby the opaque area is formed in the peripheral portion of the reproduction light incident area of the aperture forming means. The optical pickup device according to claim 1, which is formed. 5. The optical pickup device according to claim 4, wherein the dye contained in the aperture forming means is a dye that causes a coloring reaction by a photon mode reaction. 6. The aperture formation by the control means having a colored light source that emits the colored light from an annular light emitting surface as the separate light source, and emits colored light from the colored light source. 6. The optical pickup device according to claim 4, wherein the colored light is applied to the peripheral portion in the reproduction light incident area of the means. 7. The control means includes a colored light source as the another light source for emitting the colored light, and a shield material provided in an optical path between the colored light source and the aperture forming means. The colored light emitted from the colored light source is shielded by the shield material, so that the colored light is irradiated to the peripheral portion in the reproduction light incident region of the aperture forming means. Optical pickup device. 8. The coloring matter contained in the aperture forming means irradiates colored light as light from the reproducing light source and a light source different from each other to cause a coloring reaction to form the opaque region, and It is a dye that causes a decoloring reaction by irradiating the reproduction light to form the transmission region, and the control unit irradiates the colored light to almost the entire reproduction light incident region of the aperture forming unit, The coloring reaction due to the colored light occurs in the peripheral portion of the reproduction light incident area of the aperture forming means to form the opaque area, and the decoloring reaction due to the reproduction light occurs inside the peripheral portion. The transparent region is formed by
2. The optical pickup device according to 2 or 3. 9. The optical pickup device according to claim 8, wherein the dye contained in the aperture forming means is a dye that causes a coloring reaction and an erasing reaction by a photon mode reaction. 10. The optical pickup device according to claim 1, wherein the dye contained in the aperture forming means is a photochromic dye that hardly causes coloring and decoloring due to thermal reaction. 11. The coloring matter contained in the aperture forming means exhibits a colored state which becomes an opaque region to the reproduction light at room temperature, and irradiates the decolorized light as light from the reproduction light source and another light source. Is a dye that causes an erasing reaction to form the transmission region, and the control unit irradiates the erasing light to a part of the reproduction light incident region of the aperture forming unit, or 4. The optical pickup device according to claim 1, 2 or 3, wherein decolorized light having a high light intensity is applied to the reproduction light incident area, and thereby the transmission area is formed in the reproduction light incident area of the aperture forming means. . 12. The optical pickup device according to claim 11, wherein the dye contained in the aperture forming means is a dye that causes a decoloring reaction by a photon mode reaction. 13. The dye contained in the aperture forming means is an inverse photochromic dye.
2. The optical pickup device described in 2, 3, 11 or 12. 14. The optical pickup device according to claim 1, wherein the light from the different light source has a wavelength different from that of the reproduction light. 15. An optical pickup device for irradiating an optical recording medium with reproducing light to reproduce information, comprising: a first light source for emitting the reproducing light; and a portion between the first light source and the optical recording medium. A shielding member that is provided in the forward light path and that can change the size of the light transmission region portion that transmits the reproduction light, and emits control light for controlling the size of the light transmission region portion of the shielding member. An optical pickup device including a second light source.