WO2013115113A1

WO2013115113A1 - Method for producing objective lens for optical pickup device, objective lens, and method for inspecting objective lens

Info

Publication number: WO2013115113A1
Application number: PCT/JP2013/051674
Authority: WO
Inventors: 伊藤輝彦
Original assignee: コニカミノルタアドバンストレイヤー株式会社
Priority date: 2012-01-31
Filing date: 2013-01-26
Publication date: 2013-08-08
Also published as: CN104106114A; JPWO2013115113A1

Abstract

Provided are: a method that is for producing an objective lens and that is able at a low cost and favorable precision to produce an objective lens able to be assembled to an optical pickup device; an objective lens; and a method for inspecting an objective lens. Detection light (DL) is radiated towards the second flat surface (L2) of an objective lens (OL) from a detection device (SS). The detection light (DL) is reflected off of the second flat surface (L2) and returns again to the detection device (SS), and so is received by a CCD imaging surface or the like. At such a time, if the reflected light returns to a set position on the imaging surface, it is understood that the second flat surface (L2) is parallel to the optical axis of the optical pickup device. An anti-reflection coating is not formed at the second flat surface (L2), and so the strength of the reflected light from the second flat surface (L2) increases and it is possible to perform favorably precise detection.

Description

Manufacturing method of objective lens for optical pickup device, objective lens, and inspection method of objective lens

The present invention relates to a method for manufacturing an objective lens for an optical pickup device, an objective lens, and an inspection method for the objective lens.

In recent years, in an optical pickup device, a laser light source used as a light source for reproducing information recorded on an optical disc and recording information on the optical disc has been shortened. For example, a wavelength 380 such as a blue-violet semiconductor laser is used. A laser light source of ˜420 nm has been put into practical use. When these blue-violet laser light sources are used, it is possible to record 15 to 20 GB of information on an optical disk having a diameter of 12 cm when an objective lens having the same numerical aperture (NA) as that of a DVD (digital versatile disk) is used. When the numerical aperture NA of the objective lens is increased to about 0.8, information of 23 to 25 GB can be recorded on an optical disk having a diameter of 12 cm.

BD (Blu-ray Disc) is an example of an optical disc that uses an objective lens having a numerical aperture NA of 0.8 or more as described above. Since the coma generated due to the tilt (skew) of the optical disk increases, the BD has a thinner protective substrate (0.1 mm with respect to 0.6 mm of DVD) than the case of the DVD cage, and is caused by skew. The amount of coma is reduced.

However, even if the protective substrate thickness of the BD is reduced in this way, if an optical axis is tilted when an objective lens having a numerical aperture NA of 0.8 or more is attached to the optical pickup device, there is a possibility that coma aberration cannot be ignored. is there. Therefore, as shown in Patent Document 1, an optical pickup is used while detecting the attitude of the objective lens by irradiating a flat surface around the optical surface of the objective lens with laser light and receiving the reflected light. By attaching it to the apparatus, it is possible to adjust with precision so as to suppress coma.

Japanese Patent Laid-Open No. 2005-10307

By the way, in general, the optical surface of the objective lens is provided with an antireflection coating for preventing the reflection of a light beam having a design wavelength in order to increase the utilization efficiency of the semiconductor laser light used as the light source of the optical pickup device. However, when this antireflection coating adheres to a flat surface provided around the optical surface, there is a problem that the reflected light intensity of the laser beam for inspecting the tilt of the objective lens reflected from the flat surface is lowered. More specifically, for example, when the design wavelength of the antireflection coating is around 400 nm, if the wavelength of the laser beam for inspection is also around 400 nm, the flat surface to which the antireflection coating is attached is almost transmitted. In this case, the intensity of the reflected light is remarkably lowered, and the inspection becomes difficult. On the other hand, the use of a laser beam having a different wavelength can solve such a problem, but there is a problem that the laser used for inspection is limited and the manufacturing cost increases. In addition, in the compatible optical pickup device, in addition to the objective lens for BD, for example, an objective lens for DVD that collects a light beam of about 650 nm may be used together. If an inspection laser beam having a wavelength of around 650 nm is used in place of the laser beam, the inspection of the objective lens for BD can be performed effectively, but the inspection of the objective lens for DVD attached to the same optical pickup device becomes difficult. Therefore, there is a problem that two different laser beams must be prepared for inspection and the manufacturing cost further increases.

Thus, under the condition that the wavelength of the inspection laser beam is limited, the design wavelength of the coat coincides with the wavelength of the inspection laser beam when the antireflection coating adheres to the flat portion provided around the optical surface. Sometimes the reflection intensity becomes small, and it becomes difficult to accurately detect the tilt state of the objective lens. On the other hand, Patent Document 1 proposes not to coat the flat portion, but does not disclose a specific method for preventing the coating from being applied. Further, there is no mention of the problem in the case where a coat is applied to the flat portions on both sides in the optical axis direction.

The present invention has been made in view of the above-described problems, and provides an objective lens manufacturing method, an objective lens, and an objective lens inspection method that can manufacture an objective lens that can be assembled to an optical pickup device with low cost and high accuracy. The purpose is to do.

The objective lens manufacturing method according to claim 1 is provided around the first optical surface, the second optical surface having a smaller curvature than the first optical surface, and the first optical surface and the second optical surface. A method of manufacturing an objective lens for an optical pickup device having a flange portion,
The objective lens is provided with a second flat surface between the second optical surface and the flange portion, the second flat surface is a mirror surface, and when the objective lens is assembled to an optical pickup device, By irradiating the second flat surface with detection light and receiving the reflected light, the posture of the objective lens is detected. After forming the objective lens, the second flat surface from the flange portion side. Covering the second flat surface with a shielding member having a second opening extending to the side and exposing the second optical surface;
And a step of applying an antireflection coating to at least the first optical surface and the second optical surface.

According to the present invention, after the objective lens is molded, the first shielding member has a second opening that extends from the flange portion side to the second flat surface side and exposes the second optical surface. 2 The step of covering the flat surface and the step of applying the antireflection coating to at least the first optical surface and the second optical surface can suppress the formation of the antireflection coating on the second flat surface. Thus, when the objective lens is assembled to the optical pickup device, the amount of reflected light increases regardless of the wavelength of the detected light when the second flat surface is irradiated with the detected light and the reflected light is received. Therefore, the posture of the objective lens can be detected with higher accuracy, and the manufacturing cost can be reduced because the wavelength limitation of the detection light is relaxed. Furthermore, when the second flat surface is a mirror surface, the intensity of reflected light from the second flat surface can be improved.

According to a second aspect of the present invention, there is provided the objective lens manufacturing method according to the first aspect, wherein the flange portion has a second flange surface on the second optical surface side, and the second flat surface is It is located on the first optical surface side in the optical axis direction from the most apex of the second flange surface.

For example, when the manufactured objective lens is placed with the second optical surface facing down, the second optical surface side of the flange portion is prevented so that the second optical surface does not come into direct contact with the placement surface and is not damaged. It is possible to extend the outer peripheral portion of the lens in the optical axis direction so that the outer peripheral portion is brought into contact with the mounting surface. In this case, if the second flat surface is positioned on the first optical surface side in the optical axis direction with respect to the topmost point of the second flange surface, the second flat surface may be disposed when the objective lens is placed. Scratches on the flat surface can be suppressed. Note that “the highest vertex of the second flange surface” refers to a portion of the second flange surface that is farthest in the optical axis direction with respect to the surface vertex of the first optical surface.

According to a third aspect of the present invention, there is provided the objective lens manufacturing method according to the first or second aspect of the invention, wherein an inner peripheral edge of the second opening faces the second flat surface side in a cross section in the optical axis direction of the shielding member. It is characterized by being bent.

For example, when the outer peripheral portion of the flange portion on the second optical surface side is moved away from the second flat surface in the optical axis direction, the shielding member must avoid interference with the flange portion. The second flat surface must be effectively shielded. Therefore, the inner periphery of the second opening is bent toward the second flat surface, thereby preventing the shielding member from interfering with the flange portion and shielding the second flat surface. It can be done effectively.

According to a fourth aspect of the present invention, there is provided the objective lens manufacturing method according to any one of the first to third aspects, wherein the shielding member is not in contact with the second optical surface and the second flat surface. Features.

Thereby, damage due to the shielding member coming into contact with the second flat surface and the surface of the other objective lens can be avoided, and a decrease in the intensity of reflected light on the second flat surface can be suppressed.

According to a fifth aspect of the present invention, there is provided the objective lens manufacturing method according to any one of the first to fourth aspects, wherein the shielding member has a tapered shape on the outer side in the optical axis direction with respect to the inner periphery of the second opening. It is characterized by having.

The outer side of the inner periphery of the second opening is tapered, so that when the antireflection coating is attached, the shielding member can be shaded so that insufficient adhesion to the second optical surface or the like does not occur.

The objective lens manufacturing method according to claim 6 is characterized in that, in the invention according to any one of claims 1 to 5, the width of the second flat surface is 0.16 to 0.45 mm.

When the width of the second flat surface is 0.16 mm or more, the possibility of difficulty in adjustment when reflecting the detection light is avoided, and when it is 0.45 mm or less, the outer diameter of the objective lens is reduced. Contributes to miniaturization of the optical pickup device without becoming too large. Moreover, it is more preferable that the width of the second flat surface is 0.2 mm or more because the detection light can be more reliably reflected.

According to a seventh aspect of the present invention, there is provided the objective lens manufacturing method according to any one of the first to sixth aspects, wherein 90% or more of the second flat surface is projected when the shielding member is projected in the optical axis direction. It is characterized by covering.

When the shielding member covers 90% or more of the second flat surface, the processing of the shielding member becomes easier and the tip of the shielding member becomes easier than when the entire surface (100%) is covered exactly. It is easy to suppress contact with the second optical surface. In addition, when the shielding member covers 90% or more of the second flat surface, the intensity of the reflected light from the second flat surface necessary for detecting the posture of the objective lens can be ensured.

An objective lens manufacturing method according to an eighth aspect of the present invention is the invention according to any one of the first to seventh aspects, in which the second opening of the shielding member is projected when the shielding member is projected in the optical axis direction. The periphery is located outside the second optical surface in the direction perpendicular to the optical axis.

An antireflection coating on the second optical surface without covering the second optical surface by positioning the inner peripheral edge of the second opening of the shielding member outside the second optical surface in the direction perpendicular to the optical axis. The lack of formation can be avoided.

The objective lens manufacturing method according to claim 9 is the invention according to any one of claims 1 to 8, wherein the objective lens has a first flat surface between the first optical surface and the flange portion. The first flat surface is a mirror surface, the flange portion has a first flange surface on the first optical surface side, and the shielding member is on the first flat surface side from the flange portion side. And has a first opening that exposes the first optical surface, and when the shielding member is projected in the optical axis direction, the inner periphery of the first opening is on the first flange surface. It is located in.

In the case of an objective lens with a high numerical aperture, the radius of curvature of the first optical surface on the light source side of the optical pickup device is small and often protrudes in the optical axis direction. The first optical surface protrudes from the opening of the light shielding member on the side. Therefore, if the inner peripheral edge of the first opening of the shielding member is too close to the optical axis, the shielding member and the first optical surface may come into contact with each other. Further, the shadow of the inner peripheral edge of the first opening of the shielding member may cause insufficient formation of the antireflection coating in the peripheral portion of the first optical surface. Therefore, when the shielding member is projected in the optical axis direction, an antireflection coat can be appropriately formed on the first optical surface by positioning the inner peripheral edge of the first opening on the first flange surface. .

The objective lens manufacturing method according to claim 10 is the invention according to any one of claims 1 to 8, wherein the objective lens has a first flat surface between the first optical surface and the flange portion. The first flat surface is a mirror surface, the flange portion has a first flange surface on the first optical surface side, and the shielding member is on the first flat surface side from the flange portion side. And has a first opening that exposes the first optical surface, and the inner periphery of the first opening is on the first flat surface when the shielding member is projected in the optical axis direction. It is located in.

Similarly, when the shielding member is projected in the optical axis direction, the inner peripheral edge of the first opening is positioned on the first flat surface, so that the antireflection coating can be appropriately formed on the first optical surface. Can be formed. Further, by suppressing the formation of the antireflection coating on the first flange surface, it is advantageous in accuracy when the first flange surface is used as a mounting reference surface of the optical pickup device.

The objective lens manufacturing method according to claim 11 is characterized in that, in the invention according to any one of claims 1 to 10, the numerical aperture of the objective lens is 0.6 or more or 0.8 or more. .

The objective lens of the present invention is particularly suitable for an objective lens having a numerical aperture of 0.6 or more used for an optical pickup device for DVD or an objective lens having a numerical aperture of 0.8 or more used for an optical pickup device for BD. . Since coma is proportional to the third power of the numerical aperture, when the numerical aperture has a high numerical aperture such as an objective lens having a numerical aperture of 0.6 or more, the present invention is more useful because high assembly accuracy is required. In particular, in the case of a 3-compatible lens that is compatible with three types of discs of BD, DVD, and CD, since the tolerance of coma is narrow, a higher assembly accuracy is required, so that the present invention is particularly useful. It becomes.

The objective lens according to claim 12, wherein a first optical surface, a second optical surface having a smaller curvature than the first optical surface, and a flange provided around the first optical surface and the second optical surface. An objective lens for an optical pickup device having a portion,
The objective lens includes a first flat surface between the first optical surface and the flange portion, and a second flat surface between the second optical surface and the flange portion. The flat surface and the second flat surface are mirror surfaces, and an antireflection coating is formed on the first optical surface, the second optical surface, and the first flat surface, but the antireflection coating is formed on the second flat surface. When the objective lens is assembled to the optical pickup device, the second flat surface is irradiated with detection light and the reflected light is received to detect the posture of the objective lens. It is characterized by becoming.

According to the present invention, since the antireflection coating is formed on the first optical surface, the second optical surface, and the first flat surface, the light use efficiency can be improved, and the second flat surface. Since the antireflection coating is not formed on the optical pickup device, when the objective lens is assembled to the optical pickup device, the second flat surface is irradiated with the detection light, and when the reflected light is received, the wavelength of the detection light is set. Regardless, since the amount of reflected light increases, the posture of the objective lens can be detected with higher accuracy, and the wavelength limit of the detection light is relaxed, so that the manufacturing cost can be reduced. Furthermore, when the second flat surface is a mirror surface, the intensity of reflected light from the second flat surface can be improved.

According to a thirteenth aspect of the present invention, in the invention according to the twelfth aspect, the flange portion includes a first flange surface on the first optical surface side and a second flange surface on the second optical surface side. And the first flat surface is located closer to the second optical surface in the optical axis direction than the highest vertex of the first flange surface, and the second flat surface is the highest vertex of the second flange surface. It is located on the first optical surface side in the optical axis direction.

For example, when the manufactured objective lens is placed with the second optical surface facing down, the second optical surface side of the flange portion is prevented so that the second optical surface does not come into direct contact with the placement surface and is not damaged. By projecting the outer peripheral portion of the second flange surface in the optical axis direction, the second flange surface can be brought into contact with the mounting surface. In this case, if the second flat surface is positioned on the first optical surface side in the optical axis direction with respect to the topmost point of the second flange surface, the second flat surface may be disposed when the objective lens is placed. Scratches on the flat surface can be suppressed. Further, the first flat surface is positioned closer to the second optical surface in the optical axis direction than the top of the first flange surface, so that the first flange surface is used as an attachment reference surface for the optical pickup device. In this case, interference and the like are reduced, which is advantageous. Note that “the most apex of the first flange surface” refers to a portion of the first flange surface that is farthest in the optical axis direction from the surface apex of the second optical surface.

The objective lens according to claim 14 is the objective lens according to claim 12 or 13, wherein the width of the second flat surface is 0.16 to 0.45 mm.

When the width of the second flat surface is 0.16 mm or more, the possibility of difficulty in adjustment when reflecting the detection light is avoided, and when it is 0.45 mm or less, the outer diameter of the objective lens is reduced. Contributes to miniaturization of the optical pickup device without becoming too large.

The objective lens inspection method according to claim 15 is provided around the first optical surface, the second optical surface having a smaller curvature than the first optical surface, and the first optical surface and the second optical surface. An inspection method of an objective lens for an optical pickup device having a flange portion formed,
The objective lens includes a first flat surface between the first optical surface and the flange portion, and a second flat surface between the second optical surface and the flange portion. The flat surface and the second flat surface are mirror surfaces, and an antireflection coating is formed on the first optical surface, the second optical surface, and the first flat surface, but the antireflection coating is formed on the second flat surface. Does not form,
When the objective lens is assembled to the optical pickup device, the second flat surface is irradiated with detection light having a wavelength of 630 to 670 nm or 380 to 420 nm, and the reflected light is received to detect the posture of the objective lens. It is characterized by doing.

According to the present invention, since the antireflection coating is formed on the first optical surface, the second optical surface, and the first flat surface, the light use efficiency can be improved, and the second flat surface. Since the antireflection coating is not formed on the optical pickup device, when the objective lens is assembled to the optical pickup device, the second flat surface is irradiated with the detection light, and when the reflected light is received, the wavelength of the detection light is set. Regardless, since the amount of reflected light increases, the posture of the objective lens can be detected with higher accuracy, and the wavelength limit of the detection light is relaxed, so that the manufacturing cost can be reduced. Furthermore, regardless of the type of antireflection coating formed on the objective lens, the intensity of the reflected light can be secured when the second flat surface is irradiated with detection light. Furthermore, when the second flat surface is a mirror surface, the intensity of reflected light from the second flat surface can be improved.

In this specification, the objective lens refers to an optical system that is disposed at a position facing the optical disk in the optical pickup device and has a function of condensing a light beam emitted from the light source onto the information recording surface of the optical disk. Therefore, in this specification, the numerical aperture NA on the optical information recording medium side (image side) of the objective lens refers to the numerical aperture NA of the lens surface closest to the optical information recording medium side of the objective lens. . Further, in this specification, the required numerical aperture NA is the numerical aperture specified by the standard of each optical information recording medium, or the information of the information depending on the wavelength of the light source used for each optical information recording medium. It is assumed that the numerical aperture of an objective lens having a diffraction limit performance capable of obtaining a spot diameter necessary for recording or reproduction is shown. The flange portion is a portion that is disposed around the optical surface and is used for attaching an objective lens to the optical pickup device. Moreover, a mirror surface means the surface whose surface roughness Ry is 0.3 micrometer or less. In addition, as a mirror surface, it is more preferable that surface roughness Ry is 0.1 micrometer or less. Here, the surface roughness Ry is the height from the lowest valley bottom to the highest mountain peak in the minute unevenness of the surface. Further, the first flat surface and the first flange surface may be flush with each other or may be shifted in the optical axis direction. Similarly, the second flat surface and the second flange surface may be flush with each other or may be shifted in the optical axis direction.

According to the present invention, it is possible to provide an objective lens manufacturing method, an objective lens, and an objective lens inspection method that can manufacture an objective lens that can be assembled into an optical pickup device with low cost and high accuracy.

It is the schematic of the vapor deposition apparatus of the objective lens concerning this Embodiment. It is the figure which looked at the holder holding an objective lens from the arrow II direction of FIG. It is the figure which cut | disconnected the structure of FIG. 2 by the III-III line | wire, and looked at the arrow direction. It is a figure which shows the test | inspection state at the time of attaching the objective lens OL to an optical pick-up apparatus. It is the cross-sectional schematic diagram which expanded the flange part periphery of the objective lens. It is sectional drawing of the holder 20 'holding the objective lens OL' concerning another embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of a vapor deposition apparatus for an objective lens according to the present embodiment, and FIG. 2 is a diagram of a holder for holding the objective lens as viewed from the direction of arrow II in FIG. With reference to FIG. 1 etc., the vapor deposition apparatus etc. for enforcing the manufacturing method of the objective lens which concerns on this embodiment first are demonstrated.

As shown in FIG. 1, the vapor deposition apparatus 100 supports a vapor deposition source 10 that is a film forming material source for vacuum vapor deposition, a plurality of holders 20 that hold a plurality of objective lenses, and a plurality of holders 20. Control the operation of the vapor deposition source 10, the umbrella body 30 that is rotated and inverted, the vacuum container 40 that stores the vapor deposition source 10, the umbrella body 30, the correction plate 50 that adjusts the film thickness in the meridian direction of the umbrella body 30. A vapor deposition source control unit 91 to perform operation, an umbrella body drive unit 92 for operating and driving the umbrella body 30, an atmospheric pressure control unit 93 for controlling the atmospheric pressure in the vacuum container 40, that is, a degree of vacuum, and a correction plate for adjusting the arrangement of the correction plate 50 The control part 94, the vapor deposition source control part 91, the umbrella body drive part 92, the atmospheric | air pressure control part 93, and the control part 90 which controls operation | movement of the correction plate control part 94 are provided. The objective lens that is the target of film formation by the vapor deposition apparatus 100 is a plastic lens having a numerical aperture NA of 0.8 or more formed by injection molding using an APEL-based resin material manufactured by Mitsui Chemicals. Is used as an objective lens of an optical pickup device for BD after the film forming process.

The vapor deposition source 10 enables vacuum deposition of various film forming materials, and includes a plurality of crucible portions 10 a and an electron gun portion 10 b arranged at the bottom of the vacuum vessel 40. Here, the plurality of crucible portions 10a are supported by the turret 10d and can be switched in arrangement. Each crucible portion 10a contains an evaporating material for coating the surface of the objective lens, and the electron gun portion 10b is used for the evaporating material in a specific crucible portion 10a arranged at a deposition position by the turret 10d. An electron beam is incident. Thereby, the evaporation substance in the crucible part 10a can be heated and melted by the electron beam, and the vapor EM of the evaporation substance can be injected upward from the crucible part 10a. The vapor deposition source 10 is operated by the vapor deposition source control unit 91. In addition, a plurality of film forming materials can be coated on the surface of the objective lens by sequentially moving the plurality of crucible portions 10a to the vapor deposition position, and a multilayer film can be formed by stacking different film forming materials. A coating can be formed.

The holder 20 has a rectangular plate-like outer shape as shown in FIG. 2, and holds a number of objective lenses OL arranged two-dimensionally. The holder 20 is attached to the umbrella body 30 and is disposed above the vapor deposition source 10 in a state where a large number of objective lenses OL are opposed to the vapor deposition source 10. The holder 20 can be turned upside down or upside down together with a part of the umbrella body 30 (fan-shaped part).

1, the vacuum vessel 40 supports the vapor deposition source 10 at the bottom and the umbrella 30 at the top in the internal space IS. A reversing mechanism 41 is provided on the wall surface of the vacuum vessel 40 in order to reverse a part of the umbrella 30. The vacuum vessel 40 is connected to an atmospheric pressure control unit 93 that controls the atmospheric pressure in the vacuum vessel 40. The inside of the vacuum vessel 40 is depressurized or leaked by the atmospheric pressure control unit 93.

The correction plate 50 is for adjusting the film thickness difference in the meridian direction of the umbrella body 30. The correction plate 50 is disposed between the vapor deposition source 10 and the umbrella body 30. The posture of the correction plate 50 in the vacuum vessel 40 is controlled by the correction plate control unit 94. By appropriately raising and lowering the correction plate 50, the portion of the umbrella body 30 that is behind the correction plate 50 is not vapor-deposited.

The control unit 90 controls operations of the vapor deposition source control unit 91, the umbrella body drive unit 92, the atmospheric pressure control unit 93, and the correction plate control unit 94.

FIG. 3 is a view of the configuration of FIG. 2 taken along the line III-III and viewed in the direction of the arrow. In FIG. 3, the objective lens OL is provided around the first optical surface S1, the second optical surface S2 having a smaller curvature than the first optical surface S1, and the first optical surface S1 and the second optical surface S2. And a flange portion FL. The first flange surface F1 that is the end surface on the first optical surface side of the flange portion FL and the second flange surface F2 that is the end surface on the second optical surface side of the flange portion FL are orthogonal to the optical axis X, respectively. ing. The outer peripheral surface of the flange part FL is PL.

The objective lens OL has a first flat surface L1 that is a mirror surface and a first inclined surface C1 between the first optical surface S1 and the first flange surface F1 of the flange portion FL so that adjacent portions are in contact with each other. In addition, a second flat surface L2 that is a mirror surface and a second inclined surface C2 are provided between the second optical surface S2 and the second flange surface F2 of the flange portion FL so that adjacent portions are in contact with each other. is doing. The surface roughness Ry of the first flat surface L1 and the second flat surface L2, which are mirror surfaces, is 0.1 μm or less, respectively. The first flat surface L1 and the second flat surface L2 are orthogonal to the optical axis X, respectively. In the present embodiment, the flange portion FL has the largest thickness between the first flange surface F1 and the second flange surface F2. The width of the second flat surface L2 is 0.16 to 0.45 mm.

The first flat surface L1 is positioned closer to the second optical surface S2 in the optical axis direction than the highest vertex P1 of the first flange surface F1, and the second flat surface L2 is more than the highest vertex P2 of the second flange surface F2. Is also located on the first optical surface S1 side in the optical axis direction.

The holder 20 constituting the shielding member includes a main body 21 and a lid portion 22 that is detachably attached to the main body 21. The main body 21 has a plurality of annular recesses 21a. The annular recess 21a includes a tapered inner peripheral surface 21b, a cylindrical inner peripheral surface 21c following the tapered inner peripheral surface 21c, an annular bottom surface 21d that intersects the cylindrical inner peripheral surface 21c and extends radially inward, and an annular bottom surface 21d. And an annular raised portion 21e bulging annularly with a predetermined thickness on the inner side in the radial direction. The inner peripheral edge of the annular raised portion 21e constitutes the second opening. Further, a tapered surface 21f inclined toward the second optical surface S2 is formed on the outer side in the optical axis direction of the inner peripheral edge of the annular raised portion 21e.

The lid portion 22 is a plate having an equal thickness, and has a plurality of lid portion openings (first openings) 22a facing the annular bottom surface 21d of the main body 21, respectively. A tapered surface 22b inclined toward the first optical surface S1 is formed on the outer side in the optical axis direction of the inner periphery of the lid opening 22a. The inner peripheral edge of the lid opening 22a is located on the first flange surface F1 of the objective lens OL. However, as indicated by the dotted line, the inner peripheral edge of the lid opening 22a may be positioned on the first flat surface L1.

When attaching the molded objective lens OL to the holder 20, the second flange surface F2 of the flange portion FL of the objective lens OL is brought into contact with the annular bottom surface 21d with the lid portion 22 removed from the main body 21. In this state, the outer peripheral surface PL of the flange portion FL of the objective lens OL faces or comes into contact with the cylindrical inner peripheral surface 21c. Furthermore, the objective lens OL can be held by the holder 20 by attaching the lid portion 22 to the main body 21.

At this time, in the cross section in the optical axis direction of the main body 21, the inner peripheral edge of the annular raised portion 21e is bent toward the second flat surface L2 side of the objective lens OL, but the annular raised portion 21e has the second optical surface S2. And it is non-contact with the 2nd flat surface L2. Thereby, the damage of 2nd optical surface S2 and 2nd flat surface L2 can be suppressed. Further, when the annular raised portion 21e is projected in the optical axis direction, the inner peripheral edge thereof is located outside the second optical surface S2 in the direction orthogonal to the optical axis and covers 90% or more of the second flat surface L2. Yes. Thereby, the coating of the second optical surface S2 is not disturbed. Note that a part of the entire circumference of the second flat surface L2 may be covered.

An outline of a method for manufacturing an objective lens using the vapor deposition apparatus 100 of FIG. 1 will be described. First, a large number of objective lenses OL are produced by injection molding or the like. Thereafter, as shown in FIG. 2, the individual objective lenses OL are set in the recesses of the holder 20. Thereafter, the holder 20 is attached to the umbrella body 30. At this time, the holders 20 are set so that the lid part 22 side of each holder 20 faces the vapor deposition source 10, but the objective lens OL does not fall from the main body 21 because of the lid part 22.

Furthermore, the umbrella body 30 with the holder 20 set in this way is placed under vacuum in the vacuum vessel 40 and vapor deposition is performed by the vapor EM from the vapor deposition source 10. At this time, the umbrella 30 is rotated around the rotation axis OX by the rotating device 32d, thereby improving the uniformity of film formation. At this time, since the tapered surface 22b is formed outside the inner peripheral edge of the lid portion opening 22a, a shadow is hardly generated during vapor deposition, and the coating of the first optical surface S1 is not hindered.

After a certain period of time, when the film formation on the first optical surface S1 is completed, the holder 20 is inverted 180 ° and set so that the main body 21 side of the holder 20 faces the vapor deposition source 10, The same film formation is performed. Thereby, the thin film can be formed on the second optical surface S2 in a lump.
At this time, since the tapered surface 21f is formed on the outer side of the inner peripheral edge of the annular raised portion 21e, a shadow is hardly generated during vapor deposition, and the coating of the second optical surface S1 is not hindered. However, since the second flat surface L2 is covered with the annular raised portion 21e, no coat is formed.

Thereafter, the holder 20 and the like are taken out of the vacuum container 40, and the objective lens OL after vapor deposition is taken out. Thus, the objective lens OL is completed.

FIG. 4 is a diagram illustrating an inspection state when the objective lens OL is assembled to the optical pickup device. With reference to FIG. 4, the inspection method of the present embodiment will be described. First, the first flange surface F1 and the outer peripheral surface PL of the flange portion FL are brought into contact with the lens holder HLD of the optical pickup device to hold the objective lens OL. In this state, the detection light DL having a wavelength of 630 to 670 nm or 380 to 420 nm is emitted from the detection device SS toward the second flat surface L2 of the objective lens OL.
Since the detection light DL is reflected from the second flat surface L2 and returns to the detection device SS, the detection light DL is received by a CCD or the like. At this time, if the reflected light returns to a fixed position on the imaging surface, it can be seen that the second flat surface L2 is parallel to the optical axis of the optical pickup device.

FIG. 5 is a schematic cross-sectional view enlarging the periphery of the flange portion of the objective lens, but the film thickness of the coat is different from the actual one. According to the present embodiment, since the antireflection coat CT is not formed on the second flat surface L2, the intensity of the reflected light from the second flat surface L2 by the detection light DL is increased, and accurate detection is performed. be able to. However, since the reflectance of the second flat surface L2 is not 100%, several percent of light may pass through the flat surface L2. In such a case, the transmitted light DL ′ indicated by a dotted line in FIG. 5 further enters the first flat surface L1. Here, when the antireflection coating CT is not formed on the first flat surface L1, the transmitted light DL ′ is reflected by the first flat surface L1 and emitted from the second flat surface L2, and the detection device SS (FIG. 4) may be detected, which may cause noise to be superimposed on the detection signal. On the other hand, if the antireflection coating CT is formed on the first flat surface L1, the transmitted light DL ′ is transmitted through the first flat surface L1 and does not become return light, so that erroneous detection can be suppressed. In the present embodiment, the first flat surface L1 and the second flat surface L2 are parallel, but when the first flat surface L1 and the second flat surface L2 are non-parallel, the transmitted light DL ′ is the first light. Even if it is reflected by the flat surface L1, it is more preferable because noise can be prevented from being superimposed on the detection signal.

From the viewpoint of lens molding, the first optical surface S1 and the first flat surface L1 may be formed by an integral mold. In this case, the first flat surface L1 is also formed in the same manner as the first optical surface S1. It becomes a mirror surface. When the antireflection coating CT is not formed on the first flat surface L1, and the first flat surface L1 is a mirror surface, the above-described transmitted light DL 'is more easily reflected on the first flat surface. Therefore, when the first flat surface L1 is a mirror surface, it is more effective to form the antireflection coating CT on the first flat surface L1.

The first optical surface S1 is arranged on the side closer to the laser light source for writing (recording) or reading (reproducing) when the objective lens OL is incorporated in the optical pickup device. Further, the second optical surface S2 is disposed to face the optical information recording medium (specifically, DVD and BD) when the objective lens OL is incorporated in the optical pickup device. During operation of the optical pickup device, as shown in FIG. 5, recording light WL emitted from a light source (not shown) is incident from the first optical surface S1, refracted and emitted from the second optical surface S2, and is not shown. However, since the antireflection coating CT is formed on the optical surfaces S1 and S2, reflection can be suppressed and light utilization efficiency can be increased. On the other hand, if the antireflection coating CT is formed on the first flat surface L1, transmission of unnecessary light WL ′ outside the effective diameter that is not used for recording / reproducing of the optical disc is allowed to enter the first flat surface L1. By doing so, it is possible to suppress reflection to the detector side that causes an error signal.
Although the first optical surface S1 is a smooth mirror surface, a fine structure or a fine shape which is a diffractive structure can be provided. On the other hand, the second optical surface S2 is often a smooth mirror surface having no diffractive structure. By applying an antireflection coating to the optical surfaces S1 and S2 of the objective lens OL, the transmittance increases by about 6%.

FIG. 6 is a cross-sectional view of a holder 20 'that holds an objective lens OL' according to another embodiment. In the present embodiment, the flange portion FL ′ of the objective lens OL ′ has a straight shape (equal thickness). That is, the first flange surface F1 ′ of the flange portion FL ′ is flush with the first flat surface L1 ′, and the second flange surface F2 ′ of the flange portion FL ′ is the second flat surface L2 ′. It ’s in the same state. The main body 21 of the holder 20 has a bottom surface 21d ′ facing the flange portion FL ′ that is annularly raised in accordance with the objective lens OL ′, and the inner peripheral side thereof is not in contact with the second flat surface L2 ′. is there. Note that the shape and other configurations of the lid portion 22 are the same as those in the above-described embodiment.

The present invention is not limited to the embodiments described in the specification, and includes other embodiments and modifications for those skilled in the art from the embodiments and technical ideas described in the present specification. it is obvious. The description and examples are for illustrative purposes only, and the scope of the invention is indicated by the following claims. For example, the numerical aperture NA of the objective lens may be 0.6 or more.

DESCRIPTION OF SYMBOLS 10 Deposition source 10a Crucible part 10b Electron gun part 10d Turret 20 Holder 21 Main body 21a Recessed part 21b Tapered inner peripheral surface 21c Cylindrical inner peripheral surface 21d Bottom surface 21d 'Annular bottom surface 21e Annular raised part 21f Tapered surface 22 Lid part 22a Lid part Opening 22b Tapered surface 30 Umbrella body 32d Rotating device 40 Vacuum container 41 Inversion mechanism 50 Correction plate 90 Control unit 91 Deposition source control unit 92 Umbrella body drive unit 93 Atmospheric pressure control unit 94 Correction plate control unit 100 Deposition device C1 First slope C2 First 2 slope DL detection light DL ′ transmitted light EM vapor F1, F1 ′ first flange surface F2, F2 ′ second flange surface FL, FL ′ flange portion HLD lens holder IS internal space L1, L1 ′ first flat surface L2, L2 'Second flat surface OL, OL' Objective lens OX Rotating axis PL Outer peripheral surface S1 First optical surface S2 Second optical surface S Detector CT antireflection coating WL recording light WL 'unwanted light HLD lens holder

Claims

An optical pickup device comprising: a first optical surface; a second optical surface having a smaller curvature than the first optical surface; and a flange portion provided around the first optical surface and the second optical surface. A method of manufacturing an objective lens,
The objective lens is provided with a second flat surface between the second optical surface and the flange portion, the second flat surface is a mirror surface, and when the objective lens is assembled to an optical pickup device, The posture of the objective lens is detected by irradiating the second flat surface with detection light and receiving the reflected light. After forming the objective lens, the second flat surface from the flange portion side. Covering the second flat surface with a shielding member having a second opening extending to the side and exposing the second optical surface;
A method of manufacturing an objective lens, comprising: applying an antireflection coating to at least the first optical surface and the second optical surface.
The flange portion has a second flange surface on the second optical surface side, and the second flat surface is positioned closer to the first optical surface side in the optical axis direction than the highest vertex of the second flange surface. The method of manufacturing an objective lens according to claim 1.
3. The method of manufacturing an objective lens according to claim 1, wherein an inner peripheral edge of the second opening is bent toward the second flat surface side in a cross section in the optical axis direction of the shielding member.
4. The method of manufacturing an objective lens according to claim 1, wherein the shielding member is not in contact with the second optical surface and the second flat surface.
5. The method of manufacturing an objective lens according to claim 1, wherein the shielding member has a tapered shape on the outer side in the optical axis direction with respect to the inner peripheral edge of the second opening. .
6. The method of manufacturing an objective lens according to claim 1, wherein a width of the second flat surface is 0.1 to 0.45 mm.
The method of manufacturing an objective lens according to any one of claims 1 to 6, wherein when the shielding member is projected in the optical axis direction, 90% or more of the second flat surface is covered.
The inner peripheral edge of the second opening of the shielding member is located on the outer side in the direction perpendicular to the optical axis from the second optical surface when the shielding member is projected in the optical axis direction. The manufacturing method of the objective lens of any one of these.
The objective lens is provided with a first flat surface between the first optical surface and the flange portion, the first flat surface is a mirror surface, and the flange portion is a first optical surface side first surface. The shielding member has a first opening extending from the flange portion side to the first flat surface side and exposing the first optical surface; and 9. The method of manufacturing an objective lens according to claim 1, wherein an inner peripheral edge of the first opening is positioned on the first flange surface when projected in the optical axis direction.
The objective lens is provided with a first flat surface between the first optical surface and the flange portion, the first flat surface is a mirror surface, and the flange portion is a first optical surface side first surface. The shielding member has a first opening extending from the flange portion side to the first flat surface side and exposing the first optical surface; and 9. The method of manufacturing an objective lens according to claim 1, wherein an inner peripheral edge of the first opening is positioned on the first flat surface when projected in the optical axis direction.
11. The method of manufacturing an objective lens according to claim 1, wherein the numerical aperture of the objective lens is 0.6 or more or 0.8 or more.
An objective for an optical pickup device having a first optical surface, a second optical surface having a smaller curvature than the first optical surface, and a flange portion provided around the first optical surface and the second optical surface. A lens,
The objective lens includes a first flat surface between the first optical surface and the flange portion, and a second flat surface between the second optical surface and the flange portion. The flat surface and the second flat surface are mirror surfaces, and an antireflection coating is formed on the first optical surface, the second optical surface, and the first flat surface, but the antireflection coating is formed on the second flat surface. When the objective lens is assembled to the optical pickup device, the second flat surface is irradiated with detection light and the reflected light is received to detect the posture of the objective lens. An objective lens characterized by that.
The flange portion has a first flange surface on the first optical surface side and a second flange surface on the second optical surface side, and the first flat surface is more than the highest vertex of the first flange surface. Is located on the second optical surface side in the optical axis direction, and the second flat surface is located on the first optical surface side in the optical axis direction with respect to the most apex of the second flange surface. The objective lens according to claim 12.
14. The objective lens according to claim 12, wherein a width of the second flat surface is 0.16 to 0.45 mm.
An objective for an optical pickup device having a first optical surface, a second optical surface having a smaller curvature than the first optical surface, and a flange portion provided around the first optical surface and the second optical surface. A method for inspecting a lens,
The objective lens includes a first flat surface between the first optical surface and the flange portion, and a second flat surface between the second optical surface and the flange portion. The flat surface and the second flat surface are mirror surfaces, and an antireflection coating is formed on the first optical surface, the second optical surface, and the first flat surface, but the antireflection coating is formed on the second flat surface. Does not form,
When the objective lens is assembled to the optical pickup device, the second flat surface is irradiated with detection light having a wavelength of 630 to 670 nm or 380 to 420 nm, and the reflected light is received to detect the posture of the objective lens. An inspection method for an objective lens, comprising: