JP2003067967A - Optical path forming element, its manufacturing method, optical pickup, and optical disk drive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively reduce the distance between the light source and an objective lens in an optical pickup. SOLUTION: In this optical pickup, an optical path-forming element 2 is disposed between the light source and an optical disk. And it is made one body of flat parallel transparent plates forming a straight optical path to an optical disk 6 from the light source 1. It has an optical path separating function to separate the return light flux reflected by the optical disk as one or more straight detecting optical paths to the optical detector from the straight lighting optical path, and at least, a concave lens function which strengthens the divergence of the light flux in the optical path for lighting. One or more photoreceptors 4A and 4B are formed in one body constituting the photo detector.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an optical path forming element,
The present invention relates to a method for manufacturing an optical path forming element, an optical pickup, and an optical disk device.

[0002]

2. Description of the Related Art There is a strong demand for downsizing and thinning of optical pickups for recording and reproducing information on optical disks such as CDs and DVDs. An optical pickup described in Japanese Patent Application Laid-Open No. 6-251410 is known as an optical pickup having a small and thin optical pickup.

In the optical pickup described in the publication, a surface-emitting type semiconductor laser as a light source and a photodetector are formed on a buffer layer, and the buffer layer is sandwiched between the semiconductor laser and the first glass layer. A diffraction grating is formed on the glass layer, and a condensing lens (objective lens) having a diameter of 1 mm or less formed by a grating lens is formed on the second glass layer which is formed so as to overlap with the first glass layer.

This optical pickup is compact and thin because the main part is integrated, but the thickness still needs to be about 3 mm.

In order to reduce the diameter of the light spot formed on the recording surface of the optical disk, it is necessary to reduce the geometrical optical magnification of the image formation by the objective lens and increase the numerical aperture of the objective lens.

Considering the working distance of the objective lens, the distance between the light source light emitting portion and the objective lens needs to be large to some extent, and the structure of the optical pickup described in the above publication realizes a small-diameter light spot, It is considered difficult to reduce the thickness of the optical pickup to less than 3 mm.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to effectively reduce the distance between a light source and an objective lens in an optical pickup.

[0008]

The optical path forming element of the present invention is an element "disposed between a light source and an optical disk" in an optical pickup, and has the following features. That is, the whole is "integral structure of parallel plate-shaped transparent bodies" and forms a linear illumination optical path from the light source to the optical disc. And functionally, it has at least an optical path separation function and a concave lens function. That is, the “illumination optical path” is an optical path that guides the light flux emitted from the light source to the optical disc and is linear.

The "optical path separating function" uses the optical path of the return light flux reflected by the optical disc as one or more linear detection optical paths toward the photodetector, and the linear illumination optical path (from the light source to the optical disk). It is the function of separating from the optical path. That is, the return light flux propagates along the optical path toward the detection unit due to the optical path separation function.

The "concave lens function" is a function for enhancing the divergence of the light flux that travels along the illumination optical path.

As described above, the optical path forming element is "parallel plate-shaped as a whole", but "one or more light receiving elements constituting the light detecting portion" is integrated on the surface on the light source side. .

An optical path forming element according to a first aspect of the present invention has a structure in which a portion of the single transparent body that has a concave lens function is formed on the light source side surface and a portion that has an optical path separation function is formed on the other surface. (Claim 2)

The optical path forming element according to claim 1 also has the "first
And a configuration in which the second transparent parallel plates are superposed and integrated (Claim 3). At least one surface of the "first transparent parallel plate" is formed with a "portion having a concave lens function". The "second transparent parallel flat plate" has a "portion having an optical path separating function" formed on one surface.

Further, the optical path forming element according to claim 1 has a structure in which a plurality of transparent parallel flat plates are superposed and integrated, and one of the plurality of transparent parallel flat plates is for adjusting the optical path length. Can be done ”(Claim 4). In this case, in order to adjust the optical path length, the optical path forming element is defined as "a first transparent parallel plate having a portion having a concave lens function formed on the surface on the light source side and a portion having an optical path separation function formed on the other surface". And a second transparent parallel flat plate ”. That is, the optical path forming element according to the fifth aspect can be composed of at least two transparent parallel flat plates (the first and second transparent parallel flat plates).

The optical path forming element according to claim 4 is also characterized in that "a first transparent parallel plate having a concave lens function formed on at least one surface and an optical path separation function formed on one surface. And a second transparent parallel flat plate and a third transparent parallel flat plate for adjusting the optical path length. "
It can be configured (claim 6).

The optical path forming element according to the above-mentioned claim 1 or 4 or 5 or 6 is such that "a portion that fulfills the optical path separating function is formed as a polarization hologram, and a phase difference of 1/4 wavelength is provided on the optical disk side of the polarization hologram. It is possible to have a "structure in which a layer to be provided is formed" (Claim 7).

The optical path forming element according to claim 8 forms a portion which fulfills the optical path separating function in the optical path forming element according to claim 2 or 3 as a polarization hologram, and is 1/4 on the optical disk side of the polarization hologram. It is characterized in that a layer that gives a phase difference of a wavelength is formed.
The “layer that gives a phase difference of ¼ wavelength” may be a birefringent crystal thinly cut out to form a wave plate, or may be formed as a thin film of a substance exhibiting birefringence.

The optical path forming element according to the above-mentioned claim 1 or 4 or 5 or 6 or 7 or 8 integrally includes a transparent parallel plate having a portion functioning as an objective lens on the optical disk side rather than a portion functioning as a concave lens. It may have a structure (claim 9).

The optical path forming element according to the ninth aspect of the present invention is "a transparent parallel plate having a portion functioning as an objective lens, which is transparent for performing focusing control and / or tracking control on the transparent parallel plate. The structure having the actuator functional layer ”can be provided (claim 10).

In the "transparent parallel plate having a portion functioning as an objective lens" of the optical path forming element according to claim 9 or 10, the portion functioning as an objective lens can be formed as a "solid immersion lens". Item 11). The optical path forming element according to claim 9 or 10 has "a part having the same structure as the optical path forming element according to claim 2 or 3" on the light source side with respect to the transparent parallel plate having a part functioning as an objective lens. (Claim 12).

In the optical path forming element of the above-mentioned claims 1 to 12, the position of the "portion which performs the concave lens function" may be any position between the light source and the objective lens, and the concave lens function may be provided before reaching the objective lens. It is sufficient that the portion is provided so as to increase the divergence angle of the light beam from the light source. The portion having the concave lens function may be a lens having a refracting surface or a hologram lens having a lens function by diffraction. Further, by making the lens function of the portion that performs the concave lens function an anamorphic function, it is possible to perform beam shaping by the portion that performs the concave lens function.

The optical pickup of the present invention is an "optical pickup for recording / reproducing / erasing information on / from an optical disc", and an optical path between a semiconductor laser as a light source and the optical disc is claimed. An optical path is formed by the optical path forming element according to any one of Items 1 to 12 (Claim 13).

In the optical pickup described in claim 13, the semiconductor laser and the objective lens can be "separated from the optical path forming element" (claim 14). Further, the semiconductor laser can be "integrated with the optical path forming element" (claim 15). In the case of the optical pickup according to the fifteenth aspect, when the optical path forming element according to the ninth aspect, the tenth aspect, or the eleventh aspect is used, a transparent parallel plate having a portion functioning as an objective lens from a semiconductor laser as a light source. Will be integrated as a whole.

The optical disk device of the present invention is "recording / reproducing / writing information on / from an optical disk using an optical pickup.
An optical disc device for performing one or more erasures,
An optical pickup according to any one of claims 13 to 15 is used as an optical pickup (claim 1).
6).

The invention according to claim 17 is the above-mentioned claim 3 to
A method for manufacturing the optical path forming element according to any one of 12 is characterized by the following points. That is, if necessary, a plurality of functional portions that perform a desired function are arranged in an array on a plurality of transparent parallel flat plates, and the plurality of transparent parallel flat plates are arranged such that the functional portions are linearly overlapped with each other to form a plurality of optical paths. The whole forming element is integrated so that the forming element portions are arranged, and the respective optical path forming element portions are separated from each other to form independent optical path forming elements.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. FIG. 1 (a) is an explanatory diagram showing a main part of an optical pickup using the optical path forming element according to the second aspect. Figure 1
The optical pickup shown in (a) is for performing one or more of recording, reproducing, and erasing of information on the optical disc 6.

A divergent light beam 1A emitted from a semiconductor laser 1 which is a light source passes through an optical path forming element 2 and an objective lens 3
Incident on the recording medium, condensed by the action of the objective lens 3, transmitted through the transparent substrate of the optical disc 6, and forms a light spot of a predetermined size on the recording surface.

The optical path forming element 2 has an integral structure of a parallel plate-shaped transparent body and forms a linear illumination optical path from the light source 1 to the optical disk 6. In this embodiment, the optical path forming element 2 is a "single transparent body (for example, optical quartz glass)", a portion 2A that functions as a concave lens is formed on the surface on the light source 1 side, and the other surface is formed by " The portion that performs the optical path separating function "is formed as the diffraction grating 5.
Further, on the surface of the optical path forming element 2 on the semiconductor laser 1 side,
The light receiving elements 4A and 4B are provided with their reference planes in the optical axis direction aligned with the light source side surfaces of the optical path forming element 2, and are integrated with the optical path forming element 2.

The portion 2A of the optical path forming element 2 which functions as a concave lens is a refracting surface as shown in this embodiment, but it may be a hologram lens having a lens function by diffraction or a refractive index distribution. It can also be a lens.

Since the divergence angle of the light beam emitted from the semiconductor laser 1 differs between the direction parallel to the active layer and the direction orthogonal thereto, the concave lens function of the portion 2A which performs the concave lens function is
An anamorphic function is obtained by making the curvatures of the refracting surfaces different in the directions orthogonal to each other (the direction parallel to the active layer and the direction orthogonal to each other), and the cross-sectional shape of the light flux incident on the objective lens 3 is substantially circular. It has a shape. That is, the portion 2A that functions as a concave lens has a "beam shaping function".

The light beam 1A emitted from the semiconductor laser 1 and incident on the optical path forming element 2 is diverged by the concave lens function of the portion 2A which functions as a concave lens, and passes through the optical path forming element 2.

The "returned light flux" reflected by the optical disk 6 passes through the objective lens 3 in the direction opposite to the forward path and returns to the converged light flux, and the "optical path separation function is exerted on the surface of the optical path forming element 2 on the optical disk 6 side." Diffraction grating 5 formed as
Incident on. The diffraction grating 5 has a high diffraction efficiency for ± first-order light and has a function as a lens having different powers for + 1st-order light and −1st-order light.

The return light beam is diffracted by the diffraction grating 5 as ± first-order light and separated from the illumination optical path (outward path) from the light source 1 toward the optical disk 6. The light beam 1B diffracted as the + 1st-order light is slightly weakened by "the original focusing property of the returning light beam by the objective lens 3" by the lens action of the diffraction grating 5, passes through the optical path forming element 2 while being focused, and is received on the way of focusing. It is incident on 4A.

The light beam 1C diffracted as the -1st-order light has "the original focusing property of the return light beam by the objective lens 3" and the diffraction grating 5
Is slightly strengthened by the lens action of, and is converged in front of the light receiving element 4B to be in a divergent state and enter the light receiving element 4A.
The light receiving elements 4A and 4B form a "light detecting section".

That is, the optical path forming element 2 separates the return light flux reflected by the optical disk 6 into one or more linear detection optical paths extending from the linear illumination optical path to the photodetectors 4A and 4B. It has a function and a concave lens function for strengthening the divergence of the light flux that travels through the illumination optical path, and one or more light receiving elements 4A, 4B constituting a light detection unit are integrated on the surface on the light source 1 side.

The objective lens 3 is a separate body from the optical path forming element because it is driven by focus servo and track servo by an actuation mechanism (not shown).

In the optical pickup shown in FIG. 1 (a), the focus error signal is detected by the "differential beam size method", and as described above, the diffraction grating 5 which is a portion that performs the optical path separating function is a return light beam. Is separated into two light beams 1B and 1C forming a predetermined angle with each other, and each light beam 1B and 1C is optimally designed to be condensed at different distances. Luminous flux 1
B and 1C respectively enter the light receiving elements 4A and 4B and generate various signals according to the light intensity thereof.

The track error signal detection is not shown, but the three-beam method, push-pull method, phase difference detection method, differential push-pull method (the light-receiving surfaces of the light-receiving elements 4A and 4B are divided in the track orthogonal direction). It can be performed by a known appropriate method. The focus error signal detection is not limited to the differential beam size method, but a knife edge method, an astigmatism method, or the like can be adopted, and the diffraction grating 5 can be optimized accordingly.

For example, if the focus error signal is detected by the astigmatism method and the tracking error signal is detected by the push-pull method, the diffraction grating 5 imparts "astigmatism" to the return light beam, and the light receiving element is divided into four light beams. By using the element, it is possible to generate a track error signal by the push-pull method. In this case, only one light receiving element is required.

FIG. 1B shows a comparative example with respect to the embodiment shown in FIG. In this comparative example, the optical path forming element 2a
Has no concave lens function. Therefore, the semiconductor laser 1
Since the divergence of the light flux from is not enhanced and the light flux diameter corresponding to the numerical aperture of the objective lens 3 is realized, when the optical path length between the semiconductor laser 1 and the objective lens 3 is (a) It is longer than that.

Further, in the optical path forming element 2 in the embodiment of FIG. 1A, the concave lens function of the portion 2A which performs the concave lens function is anamorphic and has a "beam shaping function", but in FIG. The optical path forming element 2a cannot have such a beam shaping function, and when beam shaping is necessary, it is necessary to separately provide a beam forming means,
Optical pickups tend to be complicated, large, and expensive.

On the other hand, in the optical pickup of FIG. 1A, since the optical path forming element 2 has a concave lens function, when the NA (numerical aperture) of the objective lens 3 on the optical disk side is fixed, the focus of the objective lens 3 is fixed. The distance can be shortened, the optical path length between the light source 1 and the objective lens 3 can be effectively shortened, and the optical pickup can be made thinner.

The light receiving elements 4A and 4B used in the optical pickup of FIG.
The reference planes A and 4B in the optical axis direction coincide with the surface on the light source side of the optical path forming element 2 ", but the light receiving element has a cross-sectional structure as shown in FIG. In the case of using the one having the cover glass 4a1 and the light receiving surface 4a3 in the "rear position" from the optical axis direction arrangement reference surface 4a2, the light receiving element 4a and the similar light receiving element 4b are For the optical path forming element 2, FIG.
It suffices to optimize the diffraction grating that is provided as shown in (b) and serves as a portion that fulfills the optical path separating function according to the arrangement of the light receiving elements 4a and 4b. The same applies to each of the embodiments described below.

FIG. 3 shows an embodiment of an optical pickup using the optical path forming element described in claim 3. In addition, in order to avoid complication, the same reference numerals are used throughout the drawings for components that are not likely to be confused.

The optical path forming element 20 used in this embodiment has a first transparent parallel plate 21 and a second transparent parallel plate 22. These are optical quartz glass or the like in terms of material. The first transparent parallel plate 21 has a first portion 2A1 having a concave lens function formed on the surface on the light source side, and a second portion 2A2 having a concave lens function formed on the opposite surface.

The second transparent parallel plate 22 is the objective lens 3
A diffraction grating 5, which is a "portion that performs an optical path separation function", is formed on the side surface. Further, the light receiving elements 4A and 4B forming the "light detecting section" are integrated with the "surface on the light source side" of the first transparent parallel flat plate 21.

These first and second transparent parallel flat plates 2
1, 22 are superposed on each other and integrated by adhesion or the like.

The divergent light 1A emitted from the semiconductor laser 1 as the light source passes through the optical path forming element 20 and the objective lens 3
Is incident on the optical disc 6, is condensed by the action of the objective lens 3, passes through the transparent substrate of the optical disc 6, and forms a light spot of a predetermined size on the recording surface.

The optical path forming element 20 has an integral structure of parallel plate-shaped transparent bodies (first and second transparent parallel plates are laminated and integrated), and linear illumination from the light source 1 to the optical disk 6 is provided. Form an optical path for use. Optical path forming element 20
The portions 2A1 and 2A2 formed on the surfaces of the light source side and the objective lens side and having a concave lens function are formed as refracting surfaces, but they may be hologram lenses having a lens function due to diffraction, and have a refractive index. It can also be a distributed lens. In order to shape the beam cross section of the beam emitted from the semiconductor laser 1 into a circular shape,
One or both of the concave lens functions of the portions 2A1 and 2A2 that perform the concave lens function are anamorphic functions.

The light beam 1A emitted from the semiconductor laser 1 and incident on the optical path forming element 20 is diverged by the concave lens function of the portions 2A1 and 2A2 having a concave lens function, passes through the optical path forming element 21, and further The second transparent parallel plate 22 is transmitted.

The “returned light flux” reflected by the optical disk 6 passes through the objective lens 3 in the direction opposite to the forward path and returns to a focused light flux, and is reflected on the surface of the optical path forming element 20 on the optical disk 6 side.
Diffraction grating 5 formed as a part that performs an optical path separation function
Incident on.

The detection of the returning light flux by the light receiving elements 4A and 4B constituting the photodetecting section and the actuation of the objective lens 3 are the same as those in the embodiment of FIG. 1 (a).

In the optical path forming element 2 used in the embodiment of FIG. 1 (a), a portion 2A having a concave lens function and a portion 5 having an optical path separating function are formed on both surfaces of a single transparent body. Further, since the light receiving elements 4A and 4B are integrated, it is necessary to accurately adjust the positional relationship between the portion 2A that performs the concave lens function, the portion 5 that performs the optical path separating function, and the light receiving elements 4A and 4B. .

On the other hand, in the optical path forming element 20 used in the embodiment shown in FIG. 3, the portion 2 having a concave lens function is used.
A1 and 2A2 are formed on the first transparent parallel plate 21, and the portion 5 that performs the optical path separating function is formed on the second transparent parallel plate 22. Therefore, after separately producing the portions that perform these functions, The positional relationship can be optimized by aligning them with each other, and the positional relationship of the portions 2A1, 2A2, 5 can be easily obtained with high accuracy.

Further, since the portion having the concave lens function and the portion having the optical path separating function are formed as transparent parallel flat plates which are different from each other, the formation is easy. Further, since the portion that performs the concave lens function is formed by the two portions 2A1 and 2A2, the negative power of the individual portions 2A1 and 2A2 can be reduced, and these portions can be easily formed.

The optical pickup shown in FIG. 4 is a modified example of the embodiment shown in FIG. 3, and constitutes an optical path forming element.
The first transparent parallel plate 21A among the two sheets of transparent parallel plates 21A and 22 has a portion 2A21 (having an anamorphic lens action for beam shaping) having a concave lens function only on the objective lens 3 side. Has been formed.

The optical pickup of the embodiment shown in FIG. 5 is an example using the optical path forming element according to the fourth and fifth aspects. The optical path forming element in this embodiment is formed by superposing (by bonding or the like) a plurality of transparent parallel flat plates 22A and 23 (of optical quartz glass or the like) and integrating them, and one of the plurality of transparent parallel flat plates is "For adjusting the optical path length". That is, in the optical path forming element, a portion 2A3 (having an anamorphic function for beam shaping) having a concave lens function is formed on the surface on the light source 1 side, and a portion (diffraction grating) having an optical path separating function is formed on the other surface. ) 5 is formed on the first transparent parallel plate 22A and the second transparent parallel plate 23 for adjusting the optical path length.

The second transparent substrate 23 is the first transparent substrate 2
It is provided closer to the light source 1 than 2A, and the light receiving elements 4A and 4B are integrated. The divergent light beam emitted from the semiconductor laser 1 passes through the second transparent parallel flat plate 23 and serves as the "concave lens function" 2A of the first transparent parallel flat plate 22A.
The divergence is strengthened by the action of 3, and the light is emitted from the first transparent parallel plate 22A, and the action of the objective lens 3 forms a light spot on the recording surface of the optical disc 6.

The light beam reflected by the optical disk becomes a return light beam and passes through the objective lens 3 and then the first transparent parallel plate 22A.
And is incident on the light receiving elements 4A and 4B. The detection of the returning light flux by the light receiving elements 4A and 4B forming the light detection unit and the actuation of the objective lens 3 are the same as those in the embodiment of FIG.

The second transparent parallel plate 23 is a light receiving element 4A,
4B is integrated with the first transparent parallel plate 22A.
Since it is a separate body from the light receiving elements 4A and 4B, the portion 2A3 that performs the concave lens function and the portion 5 that performs the optical path separation function
It is easy to align with. In addition, by adjusting the thickness of the second transparent parallel plate 23, the optical path length between the portion 5 that performs the optical path separating function and the light receiving elements 4A and 4B can be easily and appropriately adjusted.

The optical pickup of the embodiment shown in FIG. 6 is an example using the optical path forming element according to the fourth and sixth aspects. The optical path forming element in this embodiment includes a plurality of transparent parallel flat plates 22A, 23 (made of optical quartz glass or the like),
One of the plurality of transparent parallel plates is "for adjusting the optical path length", which is formed by stacking 24 (by bonding or the like) and integrating them.

That is, the optical path forming element has the first portion 2A3 having a concave lens function formed on at least one surface thereof.
22A, a second transparent parallel flat plate 24 having a portion 5 having an optical path separating function formed on one surface thereof, and a third transparent parallel flat plate 23 for adjusting the optical path length.

The optical path forming element in the optical pickup shown in FIG. 6 is a modification of the optical path forming element shown in FIG.
In the optical path forming element of "the first transparent parallel plate 22A
The diffraction grating 5 "formed on the second transparent parallel flat plate 24 is formed on one surface of the second transparent parallel flat plate 24.
It has a structure in which 4, 23 are overlapped and integrated.

By doing so, the transparent parallel plate 22A having the portion 2A3 having the concave lens function and the transparent parallel plate 24 having the portion 5 having the optical path separating function are formed.
Since the light receiving elements 4A and 4B are integrated with the transparent parallel plate 23 having a function of adjusting the optical path length, these can be independently and easily manufactured, and the parts that perform the respective functions can be easily manufactured. Positioning is also easy.

The operation of the optical pickup is the same as that of the embodiment shown in FIGS. 1 and 3 to 5.

The optical pickup of the embodiment shown in FIG. 7 is an example using the optical path forming element according to the seventh aspect. The optical path forming element used in the optical pickup of FIG.
This is a modification of the "portion (the portion where the diffraction grating 5 is formed)" of the second transparent parallel plate 24 in the optical path forming element shown in FIG.

That is, in the optical path forming element shown in FIG.
The "portion that performs the optical path separation function" is formed as the polarization hologram 5A on the second transparent parallel plate 24A, and the layer 25 that gives "a phase difference of 1/4 wavelength" to the optical disk 6 side than the polarization hologram 5A is formed. Has been done.

Since the divergent light beam 1A emitted from the semiconductor laser 1 is in a substantially linear polarization state polarized in the direction parallel to the active layer, the diffractive action is "for the light beam from the semiconductor laser 1 side. Polarization hologram 5 to "do not work"
By forming A, the light flux from the light source side can be made incident “substantially all” on the objective lens 3, and a bright light spot can be formed on the recording surface of the optical disc 6.

The return light beam reflected by the optical disc 6 is transmitted back and forth through the layer 25 so that the polarization direction is rotated 90 degrees from the forward path and is incident on the polarization hologram 5A, and the diffraction action and lens action of the polarization hologram 5A. The light paths are received and separated, and the light is incident on the light receiving elements 4A and 4B.
In this way, by using the polarization hologram as the portion that performs the optical path separation function and using the “layer that gives a phase difference of ¼ wavelength”, the light utilization efficiency in the optical pickup operation is effectively increased, and the good optical pickup operation is performed. Can be realized.

The same applies to the embodiments described below, but if the portion that fulfills the optical path separating function is formed as a polarization hologram, the utilization efficiency of light is good as described above, so that information is recorded with a small "light source light output".・ Regeneration can be performed and energy can be saved. Further, since the light utilization efficiency is high, a large focused spot intensity can be obtained, and information recording / reproduction at high linear velocity becomes possible. Since the amount of light received by the light receiving element is large, the S / N ratio in photoelectric conversion is improved, and higher quality recording / reproduction of information becomes possible.

The optical pickup of the embodiment shown in FIG. 8 is an example in which the optical path forming element described in claim 8 is used. The optical path forming element in this embodiment has the structure shown in FIG.
In the embodiment of the above, in the first transparent parallel flat plate 21 and the second transparent parallel flat plate 22 constituting the optical path forming element,
It is an example in which the portion of the second transparent parallel plate is modified.

The first transparent parallel flat plate 21 is formed of optical quartz glass or the like, as in FIG. 3, and has a first portion 2A1 serving as a concave lens function formed on the surface on the light source side and on the opposite surface. Is a second part 2 which functions as a concave lens
A2 is formed.

In the second transparent parallel flat plate 22B made of optical quartz glass or the like, the "portion which fulfills the optical path separating function" is formed as the polarization hologram 5A on the surface on the objective lens 3 side, and "on the optical disk 6 side" than the polarization hologram 5A. A layer 25 that gives a “phase difference of ¼ wavelength” is formed. The light receiving elements 4A and 4B forming the "light detecting section" are integrated with the "surface on the light source side" of the first transparent parallel flat plate 21. The first and second transparent parallel flat plates 21 and 22B are overlapped with each other and integrated by adhesion or the like.

The optical pickup operation is the same as that of the embodiment of FIG. 3, but the detection of the return light flux is the same as that of the embodiment of FIG. 7, and like the case of the embodiment of FIG.
The utilization efficiency of the light emitted from the light source can be effectively increased.

A polarization hologram is formed in place of the diffraction grating 5 in the optical path forming element 2 of the optical pickup of FIG. 1 (a), and a layer for giving "a phase difference of 1/4 wavelength" to the optical disk side of the polarization hologram is provided. It goes without saying that the formed optical path forming element can be used.

The optical pickup according to the first embodiment shown in FIG. 9 is a modification of the optical pickup shown in FIG. 7. The objective lens 3 in the optical pickup shown in FIG. The flat plate 30 "is integrated with the layer 25 by means such as adhesion.

The optical path forming element shown in FIG. 9 is an embodiment of the optical path forming element according to claim 9, and is a portion functioning as an objective lens (a portion of the objective lens which is closer to the optical disk 6 than the portion 2A3 which functions as a concave lens). A transparent parallel plate 30 having a lens surface) is integrally provided. In this case, a transparent parallel plate 30 having a portion that functions as an objective lens
Is integrated with other transparent parallel plates as a part of the optical path forming element, so focusing servo and tracking servo displace the entire optical path forming element in the optical axis direction (vertical direction in the figure) and in the direction orthogonal to the track. Can be performed by displacing the semiconductor laser 1 which is the light source.

The optical pickup of the first embodiment shown in FIG. 10 is a modification of the optical pickup of FIG. In the optical pickup of FIG. 10, the part that functions as the objective lens in the transparent parallel plate 31 that has the “part that functions as the objective lens” integrated as a part of the optical path forming element is the “solid immersion lens”.

Therefore, the optical path forming element in FIG.
This is an embodiment of the invention described in claim 12. Since the solid immersion lens is known from Japanese Patent Laid-Open No. 11-45455, detailed description thereof will be omitted here.

In the optical path forming element of the optical pickup shown in FIGS. 9 and 10, the transparent parallel flat plates 30 and 31 having a portion functioning as an objective lens are formed to have a predetermined thickness, and the other transparent parallel plate forming the optical path forming element is formed. Only by stacking on a flat plate, the light beam optical axis direction can be arranged with high accuracy.

Further, since all the optical elements have an integrated structure as an optical path forming element, the members and mechanisms for holding each optical element can be integrated into one, and since the whole is an integrated structure, the position of each part due to changes over time. There is an advantage that there is no deviation and the reliability is very high.

Further, as described in the above publication, the parallel plate type solid immersion lens can be manufactured simply, with high precision and at low cost, and since it has a parallel plate shape, it is different from other transparent parallel plate plates in forming an optical path forming element. Good affinity with etc. Further, the solid immersion lens can be miniaturized, and the optical path forming element can be made very small.

Furthermore, since the solid immersion lens can have a much larger NA than a normal convex lens, it is possible to reduce the focused spot diameter on the optical information recording medium, and therefore, "higher density" on the optical information recording medium. It is possible to record information in ".

Therefore, by forming the "portion functioning as an objective lens" by the solid immersion lens and incorporating it into the optical path forming element, it is possible to integrate the constituent elements of the optical pickup including the light receiving element. It is possible to realize an optical pickup that is compact and thin and that enables high-density recording and reproduction.

The optical pickup of the embodiment shown in FIG. 11 is a modification of the optical pickup of FIG.
A transparent actuator function layer 60 is provided between a layer 25 that gives a phase difference of four wavelengths and a transparent parallel plate 30 that forms a portion that functions as an objective lens. Therefore, the optical path forming element used in the optical pickup of FIG. 11 is an embodiment of the optical path forming element according to claim 10.

The transparent actuator functional layer 60 is for performing focusing control and / or tracking control. The surface of the actuator functional layer 60 on the side of the optical disc 6 is “an element that is movable in the direction orthogonal to the optical disc 6 to move the transparent parallel flat plate 30 and that is capable of focusing operation” or “is displaced in the direction parallel to the optical disc, It is possible to move the transparent parallel flat plate 30 in a direction orthogonal to the track "or an element capable of tracking operation", or to stack these elements so that focusing operation and tracking operation can be performed.

A piezo element, an electrostatic element, a piezoelectric element or the like can be used as a focusable element, and a well-known microactuator proposed recently can be used as a tracking element.

In the optical pickups of FIGS. 9 and 10, since the transparent parallel plate having the portion functioning as the objective lens has an integral structure with the optical path forming element, the entire optical path forming element is displaced and servo-driven by the actuation mechanism. However, it is difficult to operate at high speed because the driving weight is large. However, if the actuator function layer is provided as a part of the optical path forming element as in the optical pickup of FIG. 11, the entire optical path forming element is driven. Since it is not necessary to drive, only the portion laminated on the optical disc side of the actuator function layer needs to be driven, so that the movable portion is light and high-speed operation is possible.

FIG. 12 shows a modified example of the optical pickup shown in FIG. 10. In the structure of the optical path forming element shown in FIG. 10, a first transparent parallel flat plate 22A having a portion 2A3 having a concave lens function is formed on at least one surface thereof. The actuator function layer 60 is provided between the first transparent parallel plate 24A and the second transparent parallel flat plate 24A, which is formed as a polarization hologram and has a portion 5A having an optical path separating function. FIG. 13 shows a first embodiment of the optical pickup according to the fifteenth aspect. Figure 1
3 (a), the first transparent parallel plate 21, the second parallel plate 22B, the layer 25 for providing a phase difference of 1/4 wavelength and the polarization hologram 5A of the optical path forming element are shown in FIG.
It is the same as that of the optical pickup shown in.

A semiconductor laser chip 1 as a light source and two light receiving elements (each light receiving surface is shown by reference numerals 4A1 and 4B1)
Integrated light receiving and emitting element 1 in which the above is integrally formed on one substrate
00 was bonded or adhered to the optical path forming element to be integrated. FIG. 13C is a cross-sectional view taken along line CC of FIG. 13B. The semiconductor laser 1 emits a light beam toward the reflection surface formed on the substrate, and the light beam reflected by the reflection surface is the first light beam.
It is incident on the transparent parallel plate 21 of.

The optical pickup according to the first embodiment shown in FIG. 14 is obtained by replacing the light source and the two light receiving elements in the optical pickup shown in FIG. 12 with the integrated light receiving and emitting element 100 shown in FIG. is there.

In the optical pickups of FIGS. 13 and 14, the semiconductor laser 1 and the two light receiving elements are integrally formed and integrated with the optical path forming element, so that the optical pickup can be realized in a very small and thin shape. . In addition, the integration makes it possible to realize a highly reliable optical pickup without the positional deviation of each part due to environmental changes and aging. Especially, in the optical pickup shown in FIG. 14, the above effect is remarkable.

The optical pickup shown in FIG. 14 can have a total thickness of about 2 mm, and is suitable as a "floating type optical pickup" in addition to the one driven by a carriage or a swing arm.

The optical path forming element in each of the above-described embodiments is an "optical path forming element provided between the light source and the optical disk" in the optical pickup, and has an integrated structure of a parallel plate transparent body. A linear illumination optical path from the light source 1 to the optical disc 6, and at least one linear detection optical path for returning the return light flux reflected by the optical disc 6 from the linear illumination optical path to the photodetection unit. At least one light receiving element 4 which forms a photodetector on the surface on the light source side, and which has at least a function of separating an optical path and a concave lens function of strengthening the divergence of a light beam traveling in the illumination optical path.
This is a combination of A and 4B (Claim 1).

In the optical path forming element 2 used in the optical pickup of FIG. 1, a portion 2A having a concave lens function is formed on the light source side surface of a single transparent body, and a portion 5 having an optical path separating function is formed on the other surface. Is formed (claim 2).

The optical path forming element used in the optical pickup shown in FIGS. 3 and 4 has first transparent parallel flat plates 21 and 21 each having a portion having a concave lens function formed on at least one surface thereof.
A, and a second transparent parallel flat plate 22 having a portion 5 having an optical path separating function formed on one surface thereof, and the first and second transparent parallel flat plates are superposed and integrated ( Claim 3).

FIG. 5, FIG. 6, FIG. 7, FIG. 9, FIG.
1, the optical path forming element used in the optical pickup of FIG. 12 is formed by stacking a plurality of transparent parallel flat plates and integrating them.
One of the plurality of transparent parallel plates is the transparent parallel plate 23 for adjusting the optical path length (claim 4).

The optical path forming element used in the optical pickup shown in FIG. 5 has a portion 22 having a concave lens function on the surface on the light source side.
A where A is formed and the optical path separating function is provided on the other surface 5
And a second transparent parallel flat plate 23 for adjusting the optical path length (Claim 5), which is used in the optical pickups of FIGS. 6 and 7. The optical path forming element has a first transparent parallel plate 22A having a portion 2A3 having a concave lens function formed on at least one surface and a second transparent parallel plate having a portion 5 having an optical path separating function formed on one surface. It has a flat plate 24 and a third transparent parallel flat plate 23 for adjusting the optical path length (claim 6).

In the optical path forming element used in the optical pickup shown in FIG. 7, the portion that performs the optical path separation function is formed as a polarization hologram 5A, and a phase difference of ¼ wavelength is provided on the optical disk 6 side from the polarization hologram 5A. In the optical path forming element used in the optical pickup of FIG. 8 in which the layer 25 for giving is formed (claim 7), the portion 2A which functions as a concave lens.
1 and 2A2 are formed on the first transparent parallel plate 21, and a second transparent parallel plate 22B is formed on one surface of which a portion 5A having an optical path separating function is formed. A portion in which transparent parallel plates are superposed and integrated constitutes an optical path forming element according to claim 3, and a portion 5A which performs an optical path separating function is formed as a polarization hologram.
A layer 25 for providing a phase difference of ¼ wavelength is formed closer to the optical disc than the polarization hologram (claim 8).

The optical path forming element used in the optical pickup shown in FIGS. 9, 10, 11 and 12 is a transparent parallel plate 30 having a portion functioning as an objective lens on the optical disk 6 side from the portion functioning as a concave lens. , 31 are integrally provided (claim 9), and in the optical path forming element used in the optical pickup of FIGS. 11 and 12, on the light source side of the transparent parallel flat plates 30, 31 having a portion functioning as an objective lens, A transparent actuator function layer 60 for performing focusing control and / or tracking control is provided on the transparent parallel plate (claim 10).

In the optical path forming element used in the optical pickup shown in FIGS. 10 and 12, in the transparent parallel plate 31 having a portion functioning as an objective lens, the portion functioning as an objective lens is a solid immersion lens (claim) Item 11).

In the embodiment shown in FIGS. 7 to 14, "1"
As the layer 25 ″ that gives a phase difference of / 4 wavelength, a birefringent crystal cut out as a thin transparent parallel plate was used.

Each of the optical pickups described in the above embodiments records / reproduces / reproduces information on / from an optical disc.
An optical pickup for performing one or more erasures, wherein an optical path between the semiconductor laser 1 as a light source and the optical disk 6 is formed by the optical path forming element according to any one of claims 1 to 12 (claim 13). And FIGS. 1 and 3 to 8
In the optical pickup of (1), the semiconductor laser 1 and the objective lens 3 are separate from the optical path forming element (claim 14), but in the optical pickups of FIGS. 13 and 14, the semiconductor laser 1 is integrated with the optical path forming element. (Claim 15).

FIG. 15 schematically shows an embodiment of an optical disk apparatus (claim 16) for performing one or more of information recording / reproducing / erasing on / from the optical disk by using an optical pickup. ing.

The optical disc D is set in the holder 151 and rotated by the motor M. The “swing arm” denoted by reference numeral 152 displaces the optical pickup 154 held at the tip of the arm in the radial direction of the optical disc D by swinging. In this example, the optical pickup 154 is shown in FIG.
A piezoelectric element is used as the actuator function layer 60, and focusing control can be performed.

The optical pickup 154 comprises a swing arm 15
It is provided on the actuator 153 provided at the tip of the No. 2. The actuator 153 is the optical pickup 1
Finely move 53 in the direction orthogonal to the track. The tracking control is performed "roughly" by the swing arm 152 and finely by the actuator 153.

FIG. 16 shows a case where an optical path forming element of the type used in the optical pickup shown in FIG. 9 is manufactured as an embodiment of the “method for manufacturing an optical path forming element” described in claim 17. .

Reference numerals 161 to 164 all represent transparent parallel plates. The transparent parallel plate 161 is formed with a two-dimensional matrix in which the portion that performs the optical path length adjusting function is formed.
The transparent parallel plate 162 has two concave lens functions.
It is formed into a three-dimensional matrix. Further, the transparent parallel plate 163 is formed in a two-dimensional matrix with a portion that performs an optical path separation function, and the transparent parallel plate 164 is formed in a two-dimensional matrix with a portion that functions as an objective lens.

These transparent parallel plates 161 to 164 have two
The optical path forming element array 165 is integrated as a whole by bonding or the like so that the respective functional portions formed in the three-dimensional matrix form overlap each other linearly. In the optical path forming element array 165, since the optical path forming element portions are arrayed, each optical path forming element is cut out to form an independent optical path forming element 166.

Since a plurality of functional portions are formed in a two-dimensional array, they are laminated and integrated, and then cut out, the mass productivity is high, and alignment can be performed for a plurality of elements in one step. It is possible to manufacture a highly accurate optical path forming element with little variation.

[0111]

As described above, according to the present invention, a novel optical path forming element, a method of manufacturing an optical path forming element, an optical pickup, and an optical disk device can be realized. The optical path forming element of the present invention has a portion that performs a concave lens function,
Since it has the function of enhancing the divergence of the light flux from the light source, it is possible to effectively shorten the optical path length from the light source to the objective lens.

Such an optical path forming element can be manufactured in large quantity and at low cost by the manufacturing method of the present invention. The optical pickup of the present invention can be formed thin and compact by using the optical path forming element, and therefore, the optical disc device using such an optical pickup can be realized compactly.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of an optical pickup together with a comparative example.

FIG. 2 is a diagram for explaining another example of the light receiving element and a mounting state to the optical path forming element.

FIG. 3 is a diagram showing another embodiment of the optical pickup.

FIG. 4 is a diagram showing another embodiment of the optical pickup.

FIG. 5 is a diagram showing another embodiment of the optical pickup.

FIG. 6 is a diagram showing another embodiment of the optical pickup.

FIG. 7 is a diagram showing another embodiment of the optical pickup.

FIG. 8 is a diagram showing another embodiment of the optical pickup.

FIG. 9 is a diagram showing another embodiment of the optical pickup.

FIG. 10 is a diagram showing another embodiment of the optical pickup.

FIG. 11 is a diagram showing another embodiment of the optical pickup.

FIG. 12 is a diagram showing another embodiment of the optical pickup.

FIG. 13 is a diagram showing another embodiment of the optical pickup.

FIG. 14 is a diagram showing another embodiment of the optical pickup.

FIG. 15 is a diagram showing only a main part of an embodiment of an optical disc device.

FIG. 16 is a drawing for explaining the manufacturing method of the optical path forming element.

[Explanation of symbols]

1 Light source (semiconductor laser) 2 Optical path forming element 2A A part that functions as a concave lens 3 Objective lens 4A, 4B light receiving element 5 Portion that fulfills the optical path separation function (diffraction grating) 6 optical disks

Claims (17)

[Claims] 1. An optical path forming element provided between a light source and an optical disk in an optical pickup, which is an integrated structure of a parallel plate-shaped transparent body, and has a linear illumination optical path extending from the light source to the optical disk. An optical path separating function for forming the return light flux reflected by the optical disc and separating it as one or more linear detection optical paths from the linear illumination optical path to the photodetection section, and a light flux traveling through the illumination optical path. And a concave lens function for enhancing the divergence of the optical path forming element, and one or more light receiving elements constituting the photodetection section are integrated on the surface on the light source side. 2. The optical path forming element according to claim 1, wherein a surface of the single transparent body on the light source side has a portion that functions as a concave lens, and the other surface has a portion that functions as an optical path. An optical path forming element characterized by the above. 3. The optical path forming element according to claim 1, wherein a first transparent parallel plate having a concave lens function formed on at least one surface and an optical path separating function formed on one surface. Second
And a transparent parallel plate, and the first and the second transparent parallel plates are superposed and integrated with each other. 4. The optical path forming element according to claim 1, wherein a plurality of transparent parallel flat plates are laminated and integrated, and one of the plurality of transparent parallel flat plates is for adjusting an optical path length. An optical path forming element characterized by being present. 5. An optical path forming element according to claim 4, wherein a part that functions as a concave lens is formed on a surface on the light source side, and a part that functions as an optical path is formed on the other surface. And a second transparent parallel plate for adjusting the optical path length. 6. The optical path forming element according to claim 4, wherein a first transparent parallel plate having a concave lens function formed on at least one surface and an optical path separating function formed on one surface. Second
And a third transparent parallel plate for adjusting the optical path length. 7. The optical path forming element according to claim 1, 4 or 5 or 6, wherein a portion that fulfills an optical path separating function is formed as a polarization hologram, and is 1/4 closer to the optical disk than the polarization hologram.
An optical path forming element, wherein a layer that gives a phase difference of a wavelength is formed. 8. An optical path forming element provided between a light source and an optical disk in an optical pickup, wherein a portion of the optical path forming element according to claim 2 or 3 which performs an optical path separating function is formed as a polarization hologram. , 1/4 closer to the optical disk than this polarization hologram
An optical path forming element, wherein a layer that gives a phase difference of a wavelength is formed. 9. The optical path forming element according to claim 1, 4 or 5 or 6 or 7 or 8, wherein a transparent parallel plate having a portion functioning as an objective lens is integrally formed on the optical disc side with respect to the portion functioning as a concave lens. An optical path forming element having the following. 10. The optical path forming element according to claim 9, wherein a transparent parallel plate having a portion functioning as an objective lens is provided on a light source side with a transparency for performing focusing control and / or tracking control for the transparent parallel plate. An optical path forming element, which is provided with a simple actuator function layer. 11. The optical path forming element according to claim 9 or 10, wherein in the transparent parallel plate having a portion functioning as an objective lens, a portion functioning as an objective lens is formed as a solid immersion lens. Forming element. 12. The optical path forming element according to claim 9, 10 or 11, having the same structure as the optical path forming element according to claim 2 or 3 on the light source side with respect to the transparent parallel plate having a portion functioning as an objective lens. An optical path forming element having a portion. 13. An optical pickup for recording / reproducing / erasing information on / from an optical disk, wherein an optical path between a semiconductor laser as a light source and the optical disk is any one of claims 1-12. An optical pickup having an optical path formed by the optical path forming element described. 14. The optical pickup according to claim 13, wherein the semiconductor laser and the objective lens are separate from the optical path forming element. 15. The optical pickup according to claim 13, wherein a semiconductor laser is integrated with the optical path forming element. 16. An optical disk device for recording / reproducing / erasing information on / from an optical disk by using the optical pickup, wherein the optical pickup is any one of claims 13 to 15. An optical disk device characterized by using the same. 17. A method of manufacturing an optical path forming element according to any one of claims 3 to 12, wherein a plurality of transparent parallel flat plates are arranged with a plurality of functional portions that fulfill desired functions, if necessary. The plurality of transparent parallel flat plates are integrally formed so that the functional portions are linearly overlapped with each other so that the plurality of optical path forming element portions are arranged, and the respective optical path forming element portions are mutually integrated. A method for manufacturing an optical path forming element, which is separated to form an independent optical path forming element.