JP2004205928A - Optical unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an optical unit which is not influenced by the temperature of service environment with more easily manufactured constitution as an optical unit for recording and reproducing a disk using a short wavelength light source and aiming at high storage capacity. <P>SOLUTION: The optical unit where three or more optical elements are fixed and integrated and which is provided with a gas passage where gas circulates between a space surrounded in a state where the optical effective surfaces of the optical elements face to each other and the outside air is provided with a gas passage where the gas circulates between the surrounded spaces. Furthermore, the optical element has a projecting part at a circumferential part other than the optical effective surface and is positioned in the circumferential direction by the projecting part while the optical unit is provided with the gas passage where the gas circulates between the space and the outside air by the projecting part and/or a recessed part facing to the projecting part. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical unit used for an optical pickup for recording or reading information on an optical information recording medium such as an optical disk.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as an optical unit for an optical pickup for recording or reproducing a CD or a DVD, an optical unit composed of a resin-molded single lens, a glass-molded single lens, and two resin-molded lenses has been used.
[0003]
Resin-molded lenses have a lower specific gravity than glass-molded lenses, and therefore can be reduced in weight. Therefore, there is an advantage that the load on the actuator for driving the lens can be reduced, and the responsiveness can be easily improved because the moment of inertia is small.
[0004]
The present applicant relates to an optical unit for an optical pickup constituted by a plurality of optical elements, wherein air in a space surrounded by the optical elements expands and compresses in accordance with a change in the use environment temperature, and the optical element surface In contrast to the problem of pressure fluctuations and changes in the state of the optical element surface, and the problem of moisture in this space becoming saturated and condensing on the effective optical surface when the ambient temperature drops, And the same pressure, and provided with a gas flow path so that gas can flow further (for example, see Patent Document 1).
[0005]
Furthermore, in order to assemble such that deviations in optical characteristics such as astigmatism caused by errors in molding and molding of the optical element do not overlap, an optical element having a defining portion for performing positioning in the circumferential direction has also been proposed (for example, And Patent Document 2.).
[0006]
On the other hand, in recent years, there has been proposed a disk aiming at a high storage capacity using a blue-violet laser having a density of about 400 nm and having higher density pits than conventional DVDs.
[0007]
An objective lens for an optical pickup having a diffractive lens structure provided with a ring-shaped pattern for improving the diffraction efficiency for a wavelength shorter than the conventional wavelength has been proposed (for example, see Patent Document 3). Also,
[0008]
[Patent Document 1]
JP-A-2002-221649 (FIGS. 1 to 6)
[0009]
[Patent Document 2]
Japanese Patent Application Laid-Open No. 2002-228909
[Patent Document 3]
JP-A-2002-298422
[Problems to be solved by the invention]
The optical unit provided with a gas flow path described in Patent Document 1 expands and compresses in accordance with the above-mentioned change in the use environment temperature, causing a pressure change on the optical element surface and changing the state of the optical element surface. This is an effective means for solving the problem of causing moisture and the problem that water in the space surrounded by the optical element becomes saturated and dew forms on the effective optical surface.
[0012]
On the other hand, when the optical unit is configured by using three or more optical elements, the spaces surrounded by the optical elements are connected, and if there is a difference in the ventilation state between the connected spaces, the connection is performed. A temperature difference occurs between the spaces, which affects the surface accuracy of the optical element, which is an undesirable problem.
[0013]
Further, the optical unit required for the above-mentioned high storage capacity disk needs a numerical aperture larger than that of a conventional CD or DVD. Therefore, the imaging performance and the imaging position change very sensitively to the wavelength change.
[0014]
The objective lens for an optical pickup described in Patent Literature 2 which attempts to cope with the shortening of the light source wavelength by using a single diffraction lens configuration increases the error sensitivity due to the shortening of the wavelength. There is a problem that the technical difficulty at the time of molding is increased and it takes a lot of time to overcome it.
[0015]
The present invention has been made in view of the above problems, and has an easy-to-manufacture configuration as an optical unit for recording and reproducing a disk with a high storage capacity using a blue-violet laser near 400 nm, and is affected by the temperature of the use environment. It is an object of the present invention to obtain an optical unit which is not affected by light.
[0016]
[Means for Solving the Problems]
The purpose of the above is
1) An optical unit in which three or more optical elements are fixed and integrated, and a gas flow path through which gas flows is provided between a space in which the optically effective surfaces of the optical elements are opposed to each other and outside air. An optical unit, wherein a gas flow path through which gas flows between the enclosed spaces is provided,
This eliminates the effect of temperature differences caused by differences in ventilation on the surface accuracy of optical elements, regardless of whether three or more optical elements are used or if there is a space surrounded by optical elements before and after. it can.
[0017]
2) The optical unit according to 1), wherein the optical unit includes, at least on one surface thereof, an optical element having an annular group whose thickness changes stepwise as the distance from the optical axis increases.
By separating the functions into an optical element for correcting a change in the wavelength of the light source and an optical element for image formation, it is possible to easily manufacture and mold individual molds, and to achieve stable manufacturing.
[0018]
3) The gas flow path through which the gas flows through the enclosed spaces is provided at a radial position different from the gas flow path through which the gas flows between the enclosed space and the outside air when viewed from the optical axis direction. 1) or 2) optical unit,
By doing so, the effect of 1) can be further enhanced.
[0019]
4) In an optical unit in which a plurality of optical elements are fixed and integrated, and a gas flow path through which gas flows is provided between a space in which the optically effective surfaces of the optical elements are opposed to each other and outside air, At least one of the optical elements has a convex portion on a circumferential portion other than the optically effective surface, and a gas flow path through which gas flows between the convex portion and / or a concave portion facing the convex portion and outside air. An optical unit characterized by being provided;
In this way, the optical elements are positioned in the circumferential direction, and the state of the optical element surface is changed while assembling so that deviations in optical characteristics such as astigmatism caused by molding and mold errors do not overlap. And the problem of condensation on the effective optical surface can be solved.
[0020]
5) The optical unit according to 4), wherein at least one surface of the optical unit includes an optical element having an annular group whose thickness changes stepwise as the distance from the optical axis increases.
By doing so, the production and molding of individual molds can be facilitated as in 2), and stable production can be achieved.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to embodiments, but the present invention is not limited thereto.
[0022]
(First embodiment)
FIG. 1 is a side sectional view and a rear view showing a main part configuration of an optical unit according to the first invention. FIG. 1A is a side sectional view, and FIG. 1B is a rear view. FIG. 1A is a cross-sectional view taken along line PP of FIG.
[0023]
A light beam from a laser light source (not shown) passes through a beam splitter, is converted into a parallel light beam through a collimator lens, passes through a quarter-wave plate, and is a chromatic aberration correction element 11 which is one of the optical elements shown in FIG. It is configured to be incident on.
[0024]
The chromatic aberration correction element 11 has a diffraction element structure similar to that described in Japanese Patent Application Laid-Open No. 6-82725, has a plurality of stepped flat surfaces formed on the light incident side end face, and is concentric on the optical axis. Are formed as annular zones. In addition, in the following drawings including this figure, the width of the ring zone and the step are exaggerated for easy understanding.
[0025]
When the macroscopic shape of the chromatic aberration correction element is a concave flat lens, the chromatic aberration of a positive lens utilizing general refraction can be canceled, and the chromatic aberration is corrected by using the lens in combination with an objective lens for an optical disc. be able to.
[0026]
Optical elements 12 and 13 have a positive power, and these two elements constitute an imaging system. As described above, by using a configuration in which a portion related to chromatic aberration correction and image formation is separated by a function, individual molds can be easily manufactured and molded, and stable production can be achieved. Reference numeral 15 denotes an optical disk, and 15a denotes a transparent protective layer.
[0027]
The chromatic aberration correction element 11 is provided with a cutout portion 11b at a part of the circumference of a portion 11a in contact with the optical element 12, and a space surrounded by the chromatic aberration correction element 11 and the And a gas flow path through which gas flows. Similarly, the optical element 12 is also provided with a cutout portion 12b at a part of the circumference of a portion 12a in contact with the optical element 13, so that a space surrounded by the optical element 12 and And a gas flow path through which gas flows.
[0028]
Further, the optical element 12 sandwiched between the chromatic aberration correction element 11 and the optical element 13 has a through-hole 12c in a portion other than the optically effective surface. A gas flow path through which gas flows is formed between the space surrounded by the chromatic aberration correction element 11 and the optical element 12 and the space surrounded by the optical element 12 and the optical element 13 by the through hole 12c. . As shown in FIG. 1B, the position of the through hole 12c is at a radial position different from the gas flow path through which gas flows between the enclosed space and the outside air when viewed from the optical axis direction. Preferably, it is provided. Thereby, the influence on the surface accuracy of the optical element due to the temperature difference caused by the difference in ventilation can be eliminated.
[0029]
FIG. 2 is a side cross-sectional view and a rear view showing a main part configuration of another example of the first invention. FIG. 2A is a side sectional view, and FIG. 2B is a rear view. FIG. 2A is a cross-sectional view taken along line PP of FIG.
[0030]
The optical unit shown in FIG. 2 is provided with two notches 11b and 12b shown in FIG. 1 at intervals of 180 degrees. Further, the optical element 12, which is sandwiched between the chromatic aberration correction element 11 and the optical element 13, has two through holes 12c provided in a portion other than the optically effective surface at a radial position different from the cutout portion.
[0031]
The notches 11b and 12b may be provided in large numbers, for example, at intervals of 90 degrees, at intervals of 60 degrees or at intervals of 45 degrees. Similarly, a plurality of through-holes 12c may be provided, and may be formed at intervals of, for example, 90 degrees, 60 degrees, 45 degrees, or the like. It is desirable to provide at a different position in the radial direction. Further, it is needless to say that the present invention can be applied to an optical unit having three or more components that does not use a chromatic aberration correction element.
[0032]
FIG. 3 is a side sectional view and a rear view showing a main part configuration of another example of the first invention. FIG. 3A is a side sectional view, and FIG. 3B is a rear view. FIG. 3A is a cross-sectional view taken along line PP of FIG.
[0033]
In FIG. 3, the chromatic aberration correction element 11 is provided with a notch 11b, and the optical elements 12 and 13 are provided with through holes 12c and 13c at positions other than the optically effective surfaces. A gas flow path to the outside air is formed by the notch 11b and the through hole 13c, respectively, and a space surrounded by the chromatic aberration correction element 11 and the optical element 12 by the through hole 12c, and a space surrounded by the optical element 12 and the optical element 13. It is a gas flow path through which gas flows between the space and the space.
[0034]
In the example of the first embodiment described above, the optical element has been described as a three-element configuration including a chromatic aberration correction element and two lenses having positive power. However, the present invention is not limited to this. It goes without saying that the present invention can be applied to an optical element which is fixedly integrated.
[0035]
(Second embodiment)
Embodiments of the second invention will be described below.
[0036]
FIG. 4 is a diagram showing an example of the second invention. 4A is a side sectional view including the optical axis, FIG. 4B is a rear view, and FIG. 4C is a side view.
[0037]
The optical unit in FIG. 4 includes a chromatic aberration correction element 11 and an optical element 14.
As shown in FIG. 4, the chromatic aberration correction element 11 and the optical element 14 are fitted by a circumferential abutment portion 11a, so that the interval in the optical axis direction and the optical axis are aligned. Further, the chromatic aberration correction element 11 is provided with a pair of projections 11d arranged at 90 ° intervals on the outer periphery. A predetermined one of the projections 11d and a projection provided on the optical element 14 are provided. The parts 14h are assembled so as to be fitted. The convex portion 14h does not have a shape for contact as shown in the cross-sectional view in the drawing, and therefore, a gas flow path is provided between this portion, the space surrounded by the chromatic aberration correction element 11 and the optical element 14, and the outside air. It is formed.
[0038]
FIG. 5 is a three-view drawing showing the shape of the optical element 14 used in the optical unit shown in FIG. As shown in FIG. 5, the optical element 14 is formed of a resin and has a shape having a gate portion 14g and a convex portion 14h following the gate portion. The convex portion 14h partially cuts the flange portion 14f as shown in the sectional view. It has a missing shape. In the thickness direction, a step is formed so that a gap is formed in a region between the protrusions 11d of the chromatic aberration correction element 11. The gate portion 14g is cut by a cut surface (shown) before being combined with the chromatic aberration correction element 11, and has a shape shown in FIG.
[0039]
The projections 11d and the projections 14h allow the optical elements to be positioned in the circumferential direction, and can be assembled so that deviations in optical characteristics such as astigmatism caused by errors in molding and molds do not overlap. Further, the problem of changing the state of the optical element surface and the problem of dew condensation on the effective optical surface can be solved by using a gap formed between the convex portion 14h and the protrusion 11d as a gas flow path.
[0040]
FIG. 6 is a diagram showing another example of the second invention. 6A is a side sectional view including the optical axis, FIG. 6B is a rear view, and FIG. 6C is a side view. FIG. 7 is a three-view drawing showing the shape of the optical element 14 used in the optical unit shown in FIG.
[0041]
In this example, as shown in FIG. 6, the shape of the portion of the chromatic aberration correction element 11 sandwiched between the protrusions 11d is a surface continuous with the contact portion 11a, and this is used as a gas flow path.
[0042]
As shown in FIG. 7, the optical element 14 has a shape having a gate portion 14g and a convex portion 14h following it, and the convex portion 14h has a shape in which a flange portion 14f is partially cut away as shown in a sectional view. As shown in the sectional view, the thickness direction is connected to the concave portion 14i without any step. The gate portion 14g is cut by a cut surface (shown) before being combined with the chromatic aberration correction element 11, and has a shape shown in FIG. Therefore, a gap is formed as in the case of FIG.
[0043]
In the example of the second embodiment described above, an example is described in which the convex portion is provided continuously to the gate portion of the optical element 14. However, in addition to the gate portion, the cross section of the convex portion as shown in FIG. A shape may be formed and similar assembly may be performed. In addition, the protrusions 11d are arranged at 90-degree intervals, but may be set as needed, such as at 60-degree intervals and 45-degree intervals. Further, when the positioning of the chromatic aberration correcting element 11 and the optical element 14 in the circumferential direction is generally sufficient, the gate shape itself remaining after cutting the gate may be used as the positioning in the rotation direction.
[0044]
FIG. 8 is a diagram in which both the first invention and the second invention are applied to an optical unit having three optical elements.
[0045]
8, the space surrounded by the chromatic aberration correction element 11 and the optical element 12 is a space formed by the convex portion 12h, and the space surrounded by the optical element 12 and the optical element 13 is the same as the shape of the optical element 12 shown in FIG. A gas flow path with the outside is formed by a gap formed with the portion 13h, and the optical element 12 has a through hole 12c outside the optically effective range, and a gas flow path is formed between enclosed spaces. .
[0046]
Further, the protrusion 13h of the optical element 13 is fitted in the protrusion 12d of the optical element 12 for positioning in the rotational direction, and the protrusion 12h of the optical element 12 is formed as a protrusion 11d of the chromatic aberration correction element 11 (in FIG. Positioning is performed by fitting to the boss of the pin, and the three optical elements can be positioned in the rotation direction.
[0047]
【The invention's effect】
As described above, when three or more optical elements are used, there is a space surrounded by the optical elements before and after the optical elements, and it is possible to eliminate the influence on the surface accuracy of the optical elements due to a temperature difference caused by a difference in ventilation between the two. It became so.
[0048]
In addition, a convex portion is provided on a circumferential portion other than the optically effective surface, and a gas flow path through which gas flows between the convex portion and / or a concave portion facing the convex portion is provided. In the circumferential positioning of the optical elements with each other, the problem of changing the state of the optical element surface while assembling so that deviations in optical characteristics such as astigmatism generated by errors in molding and mold do not overlap, The problem of condensation on the effective optical surface can be solved.
[0049]
As a result, as an optical unit for recording and reproducing data on and from a disk aiming at a high storage capacity using a short wavelength light source, an optical element for correcting a change in the wavelength of the light source and an optical element relating to imaging are easily separated and manufactured. It is possible to obtain an optical unit having a simple configuration and not affected by the temperature of the use environment.
[Brief description of the drawings]
FIGS. 1A and 1B are a side sectional view and a rear view showing a main part configuration of an optical unit according to a first invention.
FIGS. 2A and 2B are a side cross-sectional view and a rear view showing a main part configuration of another example of the first invention.
FIG. 3 is a side sectional view and a rear view showing a main part configuration of another example of the first invention.
FIG. 4 is a diagram showing an example of the second invention.
5 is a three-sided view showing a shape of an optical element 14 used in the optical unit shown in FIG.
FIG. 6 is a view showing another example of the second invention.
FIG. 7 is a three-view drawing showing a shape of an optical element 14 used in the optical unit shown in FIG. 6;
FIG. 8 is a diagram in which both the first invention and the second invention are applied to an optical unit having three optical elements.
[Explanation of symbols]
Reference Signs List 11 chromatic aberration correction element 12 optical element 13 optical element 14 optical element 15 optical disk 15a transparent protective layer

Claims (5)

An optical unit in which three or more optical elements are fixed and integrated, and a gas flow path through which gas flows is provided between a space surrounded by the optically effective surface of the optical elements and the outside air,
An optical unit having a gas flow path through which gas flows between the enclosed spaces. 2. The optical unit according to claim 1, wherein the optical unit includes at least one surface of an optical element having an annular group whose thickness changes stepwise as the distance from the optical axis increases. 3. The gas flow path through which the gas flows through the enclosed spaces is provided at a radial position different from the gas flow path through which the gas flows between the enclosed space and the outside air when viewed from the optical axis direction. The optical unit according to claim 1, wherein the optical unit is provided. An optical unit in which a plurality of optical elements are fixed and integrated, and an optical unit provided with a gas flow path through which gas flows between a space surrounded by the optically effective surface of the optical elements and the outside air,
At least one of the optical elements has a convex portion on a circumferential portion other than the optically effective surface, and a gas flow path in which gas flows between the convex portion and / or a concave portion facing the convex portion and outside air. An optical unit comprising: 5. The optical unit according to claim 4, wherein the optical unit includes an optical element having, at least on one surface thereof, an annular zone whose thickness changes stepwise as the distance from the optical axis increases. 6.

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