JP4661841B2 - Objective lens manufacturing method and objective lens manufacturing mold - Google Patents

Description

The present invention relates to an objective lens manufacturing mold used for molding of the objective lens manufacturing method, and an objective lens to produce by injection molding and the release of the objective lens to the mold.

  Conventionally, an optical element such as an objective lens is molded by injecting a molten resin into a mold (see, for example, Patent Document 1). FIG. 17 is a diagram for explaining the molding of a conventional objective lens. As shown in FIG. 17, a conventional optical element molding method includes a mold formed of a mold 40 having a protruding portion 41 for releasing a molded product and a mold 50 having no protruding portion. After the resin is injected into the cavity E3 through the runner E1 and the gate E2 which are resin injection flow paths of the molds 40 and 50 in order, the air in the cavity E3 is exhausted from the groove E4, and the resin is solidified and molded. The mold 40 including the protruding portion 41 is moved to open the mold, and the protruding portion 41 is operated to protrude and release the molded product of the objective lens 60. At this time, a portion corresponding to the runner E1 and the gate E2 is integrally formed on the outer peripheral flange portion 63 of the optical function portion 61 of the objective lens 60, but a portion corresponding to the gate E2 in the subsequent gate cutting step. The objective lens 60 has been molded by cutting.

  The entrance surface forming part 42 of the mold 40 forms the entrance surface 61 of the objective lens 60, and the exit surface forming part 51 of the mold 50 forms the exit surface 62 of the objective lens 60. The flange forming portions 43 and 52 form the flange 63 of the objective lens 60. The incident surface 61 is provided with an optical function surface such as a lens surface and a diffraction ring zone structure by the incident surface forming unit 42.

Conventionally, there is a CD (Compact Disc) for recording and reproducing information by condensing a laser beam on an information recording surface. Recently, a DVD having a high information recording density using a laser beam having a wavelength shorter than that of a CD. (Digital Video Disc) has been implemented, and a recording medium having a higher recording density is being realized in the near future using a blue laser beam having a shorter wavelength. Therefore, in an optical pickup device that records and reproduces information on a recording medium, an objective lens that is an optical element for condensing laser light on the information recording surface of the recording medium reduces the condensing spot in order to increase the recording density. Therefore, the objective lens is required to have a high numerical aperture (NA) on the image side (recording medium side). The objective lens with a high numerical aperture has a high curvature on the incident surface of the laser light emitted from the laser light source.
Japanese Patent Laid-Open No. 2002-200508

  However, in the conventional optical element molding method using a mold, there is a problem that when an objective lens having an incident surface is molded, there is a high possibility that air will be trapped in the incident surface forming portion when the molten resin is injected. An objective lens that has accumulated air is degraded in its original optical function. In addition, it is difficult to release the molded objective lens from the mold because it requires a strong force, and the entrance surface is easily scratched or deformed due to the release by the strong force. There was a problem. An objective lens that is scratched or deformed deteriorates its original optical function.

  These problems become significant when the objective lens has a high numerical aperture. This is because a lens having a high numerical aperture has a deep entrance surface forming portion, and air is easily trapped in this portion when the molten resin is injected, and the air is difficult to be removed. For example, in FIG. 17, it becomes the structure which exhausts the air at the time of molten resin injection from the groove | channel E4 between the metal mold | dies 40 and 50, the entrance plane formation surface 42 which has the entrance surface 61 of high numerical aperture becomes deep, and the entrance plane When air is trapped in the central portion 44 at the back of the forming surface 42, the air is more difficult to be exhausted from the groove E4.

  Also, in order to release the molded product from the deep entrance surface forming part that forms the entrance surface with a high numerical aperture, the contact area between the mold and the molded product becomes larger, so a stronger force is required. The molded product is more likely to be damaged or deformed. For example, in FIG. 17, the incident surface forming surface 42 having the high numerical aperture incident surface 61 becomes deep, and a larger force is required to release the objective lens 60 of the molded product. More likely to scratch or deform.

  Further, as shown in FIG. 17, since the resin is injected from the runner E1 and the gate E2 provided at one position on the outer periphery of the incident surface 61, the filled resin is solidified on the basis of the gate E2. There is a problem that a deviation is formed in the molded product when viewed from the center of the circular incident surface 61, and the deviation causes astigmatism, coma, and the like. The above problems are not limited to the objective lens, and similar problems may occur in the molding of other optical elements. An objective lens in which astigmatism, coma aberration, and the like are formed deteriorates the original optical function.

  The subject of this invention is preventing the fall of the optical function of the optical element by which injection molding is carried out.

The invention described in claim 1
In an objective lens manufacturing method for manufacturing an objective lens for an optical pickup device having an optical function unit by injecting a molten material into a mold,
The mold has a function of forming the optical function part on the objective lens, and when the mold is opened, the mold is formed when the mold is opened with the first mold part where the molded objective lens remains. A second mold part from which the objective lens is released,
The first mold part includes a first protruding portion protruding the objective lens, the first protruding portion is provided at a position corresponding to the optical axis of the optical functional section of the objective lens, the first And having a cross-sectional area of 16% or less with respect to the area of the entrance surface of the objective lens in contact with the mold part or the area of the exit surface of the objective lens in contact with the first mold part ,
Injecting the molten material into the mold, releasing the second mold part from the molded objective lens, and opening the mold,
An objective lens said second mold portion is a release protrudes by the first protruding portion, characterized by releasing said first mold portion from the objective lens.

The invention according to claim 2 is the invention according to claim 1,
Said first mold portion has a function of forming the optically functional section on the objective lens, a second protruding portion protruding the objective lens and the second mold portion is a release,
The first mold part is released by projecting the objective lens from which the second mold part has been released by the first and second projecting parts, and the objective remaining in the second projecting part. The lens is further protruded by the first protruding portion to release the first mold portion.

The invention according to claim 3 is the invention according to claim 1 or 2,
The first projecting portion includes an optical function forming portion that forms an optical function portion of an objective lens .
The invention according to claim 4 is the invention according to any one of claims 1 to 3,
The objective lens has an annular diffraction structure.
The invention according to claim 5 is the invention according to claim 4,
The annular diffractive structure is formed by the first mold part.

The invention described in claim 6
In an objective lens manufacturing mold that molds and manufactures an objective lens for an optical pickup device that has an optical function part by injection of a molten material,
A first mold part that has a function of forming an optical function part of the objective lens and in which the molded objective lens remains in the state when the mold is opened;
A second mold part from which the molded objective lens is released when the mold is opened;
The first mold part includes a first protrusion part that protrudes an objective lens from which the second mold part is released when the mold is opened, and the first protrusion part is the optical function part. The area of the entrance surface of the objective lens in contact with the first mold part or the area of the exit surface of the objective lens in contact with the first mold part is provided at a position corresponding to the optical axis of characterized in that that have a cross-sectional area of 16% or less.

According to the first or sixth aspect of the invention, the first protruding portion that protrudes the objective lens is provided, and the first protruding portion is provided at a position corresponding to the optical axis of the optical function portion of the objective lens, It has a cross-sectional area of 16% or less with respect to the area of the entrance surface of the objective lens in contact with the first mold part or the area of the exit surface of the objective lens in contact with the first mold part . The molten material is injected, the molded objective lens is released from the second mold part, and the objective lens is protruded by the first protruding part to release the first mold part . For this reason, it is possible to easily release the objective lens , to prevent deformation of the objective lens or damage to the optical function portion, and to prevent deterioration of the optical function of the objective lens in the injection molding. Further, since the first protruding portion has a smaller cross-sectional area than the optically functional section of the objective lens, even when the contact portion of the objective lens to be molded with the first protruding part becomes to lose optical function objective When viewed from the whole lens , the decrease in optical function can be reduced.

The invention according to claim 7 is the invention according to claim 6 ,
Said first mold portion has a function of forming the optically functional section in the objective lens, a second protruding portion protruding to the second objective lens mold portion is release when the mold is opened With
The first protruding portion further protrudes the objective lens remaining in the second protruding portion.

According to invention of Claim 2 or 7 , the 2nd protrusion part is provided in the 1st metal mold | die part, and the objective lens by which the 2nd metal mold | die part was released is made into the 1st and 2nd protrusion part. The objective lens remaining in the second protruding portion is further protruded by the first protruding portion, the first mold portion is released, and the contact area between the objective lens and the first mold portion is gradually increased. Therefore, it is possible to release the objective lens more easily, and more effectively prevent the objective lens from being deformed or scratching the optical function part, and the optical function of the objective lens in the injection molding can be prevented from being lowered.

The invention according to claim 8 is the invention according to claim 6 or 7 ,
The first projecting portion includes an optical function forming portion that forms an optical function portion of an objective lens .

According to invention of Claim 3 or 8, since the 1st protrusion part has an optical function formation part, an optical function part can be formed in the contact part to the objective lens shape | molded of an optical function formation part. It is possible to prevent the optical function of the objective lens from being lowered during injection molding.
The invention according to claim 9 is the invention according to any one of claims 6 to 8,
The objective lens has an annular diffraction structure.
According to the invention of claim 4 or 9, an objective lens having an annular diffraction structure can be manufactured.
The invention according to claim 10 is the invention according to claim 9,
The annular diffractive structure is formed by the first mold part.
According to invention of Claim 5 or 10, an annular diffraction structure can be formed by the 1st metal mold | die part .

According to the first or sixth aspect of the invention, the first protruding portion that protrudes the objective lens is provided, and the first protruding portion is provided at a position corresponding to the optical axis of the optical function portion of the objective lens, The mold has a cross-sectional area of 16% or less with respect to the area of the entrance surface of the objective lens in contact with the first mold part or the area of the exit surface of the objective lens in contact with the first mold part. The molten material is injected into the mold, the molded objective lens is released from the second mold portion, the objective lens is protruded by the first protruding portion, and the first mold portion is released . Therefore, it prevents damaging the deformation or optically functional section of the objective lens can easily release the objective lens, it is possible to prevent deterioration of the optical function of the objective lens in the injection molding. Further, since the first protruding portion has a smaller cross-sectional area than the optically functional section of the objective lens, even when the contact portion of the objective lens to be molded with the first protruding part becomes to lose optical function objective When viewed from the whole lens , the decrease in optical function can be reduced.

According to invention of Claim 2 or 7 , the 2nd protrusion part is provided in the 1st metal mold | die part, and the objective lens by which the 2nd metal mold | die part was released is made into the 1st and 2nd protrusion part. The objective lens remaining in the second protruding portion is further protruded by the first protruding portion, the first mold portion is released, and the contact area between the objective lens and the first mold portion is gradually increased. Therefore, it is possible to release the objective lens more easily, and more effectively prevent the objective lens from being deformed or scratching the optical function part, and the optical function of the objective lens in the injection molding can be prevented from being lowered.

According to invention of Claim 3 or 8, since the 1st protrusion part has an optical function formation part, an optical function part can be formed in the contact part to the objective lens shape | molded of an optical function formation part. It is possible to prevent the optical function of the objective lens from being lowered during injection molding.
According to the invention of claim 4 or 9, an objective lens having an annular diffraction structure can be manufactured.
According to invention of Claim 5 or 10, an annular diffraction structure can be formed by the 1st metal mold | die part .

  Hereinafter, first, second, third, and fourth embodiments of the present invention will be described in order with reference to the drawings.

(First embodiment)
The present embodiment will be described with reference to FIGS. FIG. 1 is a view showing a cross section of the molds 10a and 20a, FIG. 2 is a view showing a cross section of the objective lens 30a emitted to the molds 10a and 20a, and FIG. FIG. 4 is a diagram showing a cross section of the objective lens 30a, FIG. 4 is a diagram showing a cross section of the objective lens 30a projected from the projecting portion 11a, and FIG. 5 is a diagram showing an incident surface 31a of the objective lens 30a. It is.

  First, features of the apparatus according to the present embodiment will be described with reference to FIGS. The objective lens 30a, which is an example of the optical element of the present embodiment, is provided in an optical pickup device that records or reproduces information on an information recording surface such as a high-density DVD that is an information recording medium having a high information recording density. It is assumed that the objective lens is used for condensing laser light on an information recording surface such as a high-density DVD. The numerical aperture (NA) on the image side (recording medium side) of the objective lens 30a is 0.8, the curvature is large, and the incident surface forming portion 12a that forms the laser light incident surface 31a in the objective lens 30a is also deepened. The numerical aperture (NA) is not limited to 0.8. For example, an objective lens having a high curvature with an NA of 0.8 or more may be used.

  The objective lens 30a is formed of an incident surface 31a, an image-side emission surface 32a of the laser beam, and a flange 33a for attaching to the optical pickup device. As shown in FIG. 1, the mold 10a (first mold part) is provided with an incident surface forming part 12a for forming the incident surface 31a and a flange forming part 13a for forming the flange 33a. The mold 20a (second mold part) is provided with an emission surface forming part 21a for forming the emission surface 32a and a flange forming part 22a for forming the flange 33a, and by the molds 10a and 20a, A runner A1 that is a molten resin introduction path and a gate A2 that is a molten resin introduction port are provided.

  The material of the objective lens 30a is a transparent resin such as plastic, and the resin is heated and melted. The molten resin is injected into the cavity A3 and solidified by cooling to injection-mold the objective lens 30a. The cavity A3 includes an incident surface forming portion 12a, a flange forming portion 13a, an exit surface forming portion 21a, and a flange forming portion 22a.

The mold 10a is provided with a deaeration hole 14a at a substantially central portion of the entrance surface 31a of the objective lens 30a (a position corresponding to the optical axis of the optical function surface of the objective lens 30a). The deaeration hole 14a is a hole that penetrates through the mold 10a, has a circular cross section, a diameter of about 0.2 [mm], and an area of about 0.13 [mm ² ]. This size is suitable for improving the air passage when the air in the cavity A3 is deaerated and is adjusted so that the molten resin does not enter the deaeration hole 14a. In addition, other sizes may be used, and the cross-sectional shape of the deaeration hole 14a is not limited to a circular shape, and may be another shape such as a triangle or a polygon. Although not shown, an injection device that injects molten resin, an intake device that intakes air (intake means), and a compressor that injects compressed air (injection means) are provided.

  Next, in the present embodiment, a method for manufacturing an objective lens 30a, which is an example of an optical element, by injection molding will be described. First, as shown in FIG. 1, the molds 10a and 20a are combined to form the runner A1, the gate A2, and the cavity A3. An intake device is connected to the deaeration hole 14a.

  And it enters into the process of injecting molten resin from an injection device via the sprue which is not illustrated. The sprue is connected to the runner A1 and the injection device, and as shown in FIG. 2, the molten resin injected from the injection device is injected into the cavity A3 through the sprue, the runner A1, and the gate A2 in this order. At the same time, the air remaining in the cavity A3 is sucked from the deaeration hole 14a by the suction means, and therefore, in the deep incident surface forming portion 12a, it is possible to prevent the accumulation of air near the central portion 34a. The surface 31a can be accurately transferred.

  After the molten resin injected into the molds 10a and 20a is solidified by cooling and the objective lens 30a is molded, the mold release process is started. At this time, a compressor is connected to the deaeration hole 14a. First, as shown in FIG. 3, the mold 10a is moved to release the mold 20a from the solidified objective lens 30a. Thereby, the emission surface 32a and the emission surface side flange 33a are released. And as shown in FIG. 4, the protrusion part 11a protrudes from the metal mold | die 10a, and the flange 33a by the side of an incident surface is released.

  And compressed air is injected from the compressor through the deaeration hole 14a, and the entrance surface 31a is released by the force of the compressed air. Although the incident surface forming portion 12a is deep and has a large contact area with the incident surface 31a, the objective lens 30a can be easily released from the protruding portion 11a without requiring a strong force. In particular, since the incident surface 31a is pushed by the compressed air, the flange 33a or the like is not forcibly pulled, and the incident surface 31a is not caught by the mold 10a, and the optical function surface is not damaged or the objective lens 30a is not deformed. .

  Finally, an unnecessary molded part formed in the runner A1 and the gate A2 is cut at a position corresponding to the gate A2, for example, thereby completing the objective lens 30a.

  As shown in FIG. 5, on the incident surface 31a of the objective lens 30a, an optical surface such as a lens surface, an annular diffraction structure, a stepped phase difference providing structure, etc. can be freely formed by the incident surface forming portion 12a. is there. However, the incident surface forming portion is not in contact with the central portion 34a of the incident surface of the objective lens 30a, and the optical function is not formed.

  However, information on the information recording surface of the recording medium can be obtained even if an optical functional surface cannot be realized in the area ratio of about 16% or less on the objective lens with reference to the area of the entrance pupil of the laser beam of the optical pickup device. The cross-sectional area of the central portion 34a (the cross-sectional area of the deaeration hole 14a) also satisfies this condition, and is generally suitable for degassing the air in the cavity and is a molten resin. Is prevented from entering the deaeration hole 14a and realizing an optical function. Of course, a configuration in which the optical functional surface is formed on the central portion 34a by shaving or polishing the central portion 34a with a cutting tool or the like after molding may be employed.

  Therefore, according to the present embodiment, the deaeration hole 14a is provided in the substantially central portion (position corresponding to the optical axis) of the incident surface forming portion 12a, and the inside of the cavity A3 is injected when the molten resin is injected into the cavity A3. Therefore, air is prevented from remaining in the objective lens 30a due to the accumulation of air in the cavity A3, and the optical function of the objective lens 30a is prevented from being lowered, and the molded objective lens 30a is separated from the mold 20a. The objective lens 30a is protruded from the mold 10a by the protruding portion 11a, and the objective lens 30a can be easily released from the mold 10a by the air in the deaeration hole 14a at the time of releasing the mold. It is possible to prevent the objective lens 30a from being deformed or scratching the optical function surface, and to prevent the optical function of the objective lens 30a from being deteriorated in the injection molding.

  Further, since the residual air in the cavity A3 is sucked from the deaeration hole 14a, it is more effectively prevented that the air remains in the objective lens 30a and the optical function of the objective lens 30a is deteriorated. Since the compressed air is injected from the hole 14a, the objective lens 30a can be released from the mold 10a more easily, and the deformation of the objective lens 30a or the damage to the optical function surface at the time of release can be more effectively prevented. It is possible to prevent the optical function of the objective lens 30a from being lowered during injection molding.

  In the present embodiment, the deaeration hole 14a that penetrates the mold 10a from the inside to the outside is provided. However, the deaeration hole that is provided inside the mold 10a and does not penetrate to the outside is provided. But you can. In this case, the suction device and the compressor cannot be connected to the non-penetrating deaeration hole, and the intake air and the compressed air cannot be ejected. However, the residual air in the cavity A3 is, as in the conventional case, the two molds 10a and 20a. Since the air is deaerated from the gaps formed in the gap and a certain amount of air is deaerated in the deaeration holes, an air pool is generated in the central portion on the incident surface side of the objective lens 30a, and the objective lens to be molded is molded. 30a prevents air from remaining and prevents the optical function of the objective lens 30a from deteriorating, and the contact area between the objective lens 30a and the mold 10a is reduced by a deaeration hole that does not penetrate, so that the mold can be easily removed from the objective lens 30a. Therefore, it is possible to prevent the objective lens 30a from being deformed or to damage the optical function part, and to prevent the optical function of the objective lens 30a from being deteriorated in the injection molding.

  Of course, a deaeration hole 14a penetrating from the inside to the outside of the mold 10a is provided, but air is removed from the deaeration hole 14a in the same manner when an intake device or a compressor is not connected to the deaeration hole 14a. As a result, air is trapped in the central portion on the incident surface side of the objective lens 30a, air is prevented from remaining in the molded objective lens 30a, and the optical function of the objective lens 30a is prevented from being deteriorated. Due to the effect that the contact area between the objective lens 30a and the mold 10a is reduced by the hole 14a and the effect that air flows from the deaeration hole 14a and the vacuum between the objective lens 30a and the mold 10a is not brought about. The mold is easily released from the lens 30a to prevent deformation of the objective lens 30a or damage to the optical function part, and the optical function of the objective lens 30a in injection molding is reduced. It is possible to prevent.

(Second Embodiment)
The present embodiment will be described with reference to FIGS. FIG. 6 is a view showing a cross section of the objective lens 30b emitted to the molds 10b and 20b, and FIG. 7 is a cross section of the objective lens 30b from which the mold 20b is released and protruded to the protruding portions 11b and 14b. FIG. 8 is a diagram illustrating a cross section of the objective lens 30b that is further protruded to the protruding portion 14b after the mold 20b is released and protruded to the protruding portions 11b and 14b. FIG. 10 is a view showing a cross section of the objective lens 30b from which the mold 20b has been released and protruded to the protruding portion 14b, and FIG. 10 is a view showing an incident surface 31b of the objective lens 30b. This embodiment has the same components as those of the first embodiment, and different parts from the first embodiment will be described in order to avoid overlapping description. In this regard, since third and fourth embodiments described later have the same components as those of the first embodiment, different portions will be described in the same manner.

  In the apparatus of the present embodiment, as shown in FIG. 6, the mold 10b includes a protruding portion 11b (second protruding portion), an incident surface forming portion 12b, a flange, as in the first embodiment. And a rod-shaped protruding portion 14b (first protruding portion) having a smaller diameter is provided at a substantially central portion of the protruding portion 11b (a position corresponding to the optical axis of the optical function surface of the objective lens 30b). It has been. As in the first embodiment, the mold 20b is provided with an emission surface forming portion 21b and a flange forming portion 22b, and similarly, with the molds 10b and 20b, a runner B1 and a gate B2 are provided. A groove B4 is formed between the mold 10b and the mold 20b.

  As in the first embodiment, the objective lens 30b is provided with an incident surface 31b, an exit surface 32b, a flange 33b, and a central portion 34b that is a contact portion between the protruding portion 14b. The cavity B3 is formed by the incident surface forming portion 12b, the exit surface forming portion 21b, and the flange forming portions 13b and 22b.

  The protruding portion 11b is provided with a protruding surface 15 (optical function forming portion) in contact with the central portion 34b of the objective lens 30b at the tip thereof. The protruding surface 15 is subjected to processing for forming an optical functional surface at the central portion 34b during the exit molding, in the same manner as the incident surface forming portion 12b forms an optical functional surface at the incident surface 31b during the exit molding. Yes.

  Next, a method for manufacturing the objective lens 30b by injection molding in the present embodiment will be described. First, as shown in FIG. 6, the molds 10b and 20b are combined to form a runner B1, a gate B2, a cavity B3, and a groove B4.

  And it enters into the process which injects molten resin from the injection device which is not illustrated via the sprue which is not illustrated. The sprue is connected to the runner B1 and the injection device, and the molten resin injected from the injection device is injected into the cavity B3 through the sprue, the runner B1, and the gate B2 in this order. The air remaining in the cavity B3 is exhausted from the groove B4.

  Then, after the molten resin injected into the molds 10b and 20b is solidified by cooling and the objective lens 30b is molded, the mold release process is started. First, the mold 10b is moved to release the mold 20b from the solidified objective lens 30b. Thereby, the emission surface 32b and the emission surface side flange 33b are released. And as shown in FIG. 7, the protrusion parts 11b and 14b are protruded simultaneously from the metal mold | die 10b, and the flange 33b by the side of an incident surface is released.

  And as shown in FIG. 8, the protrusion part 14b is further protruded from the metal mold | die 10b, and the entrance plane 31b remaining in the protrusion part 11b is released. Although the incident surface forming portion 12b is deep and has a large contact area with the incident surface 31b, the objective lens 30b can be easily released from the protruding portion 14b without requiring a strong force.

  Finally, unnecessary molding portions molded in the runner B1 and the gate B2 are cut at a position corresponding to the gate B2, for example, to complete the molding of the objective lens 30b.

  Next, another method for manufacturing the objective lens 30b by injection molding in the present embodiment will be described. First, the process until the mold 20b is released from the objective lens 30b is the same as the above injection molding method. And as shown in FIG. 9, only the protrusion part 14b protrudes from the metal mold | die 10b, and the flange 33b and the entrance plane 31b are mold-released at a stretch. Thereafter, the objective lens 30b can be easily released from the protruding portion 14b without requiring a strong force, and unnecessary molded portions formed in the runner B1 and the gate B2 are cut at positions corresponding to the gate B2, for example.

  As shown in FIG. 10, in any of the two injection molding methods of the present embodiment, an optical functional surface is formed on the incident surface 31b by the incident surface forming portion 12b, and the central portion 34b on the incident side of the objective lens 30b. In this case, since the optical functional surface is formed by the protruding surface 15, the cross-sectional area of the protruding portion 14b is not particularly limited. However, in the case of adopting a configuration in which the optical function surface of the central portion 34b is not formed on the protruding surface 15, as described in the first embodiment, the laser light from the laser light source of the optical pickup device The area ratio of the protruding surface 15 is preferably set to about 16% or less with reference to the area of the entrance pupil.

  This is due to the following reason. When the optical function is not formed in the central portion 34b of the incident surface 31b of the objective lens 30b, the laser light incident on the central portion 34b becomes unnecessary light that does not contribute to the formation of a condensed spot. Therefore, the objective lens 30b having the central portion 34b where the optical function is not formed has an amplitude filter (so-called super-resolution filter) in which the absorption of the laser beam is large at the central portion of the incident surface and decreases toward the periphery. The lens is in the same state as the lens provided in In this case, I1 (center intensity of the diffraction image) of the focused spot by the objective lens 30b is weaker than the intensity I2 of the focused spot by the objective lens having an optical function at the center due to the super-resolution phenomenon. Become. In order for the objective lens 30b to function as a diffraction limited lens, the intensity I1 is preferably 80% or more of the intensity I2. Since aberrations remain in the actually manufactured lens due to manufacturing errors, the intensity I1 is more preferably 80% or more of the intensity I2. Therefore, especially when the numerical aperture of the objective lens 30b is increased to 0.8 or more, in order for the intensity I1 to be 80% or more of the intensity I2, the central portion 34b with respect to the area of the entrance surface 31b (area of the entrance pupil plane). The area ratio is preferably 16% or less.

  Therefore, according to the present embodiment, the protruding portion 14b is provided in the substantially central portion (position corresponding to the optical axis) of the incident surface forming portion 12b, the molten resin is injected into the cavity B3, and the molded objective lens 30b. Is released from the mold 20b, and the objective lens 30b is protruded by the protruding portion 14b to release the mold 10b. Therefore, the objective lens 30b can be easily released, and the objective lens 30b is deformed or optically removed at the time of release. The functional surface is prevented from being scratched, and the protruding portion 14b has a smaller cross-sectional area than the optical functional portion of the incident surface 12b. Therefore, the objective lens 30b is brought into contact with the formed objective lens 30b. The deterioration of the optical function can be reduced. Further, the projecting surface 15b is processed to form an optical functional surface and forms a central portion 34b on which the optical functional surface is formed. Therefore, an optical functional surface is also formed on the central portion 34b, and an objective lens in injection molding is formed. Degradation of the optical function of 30b can be prevented.

  Further, when the mold 10b is released by the two-stage protrusion in which the objective lens 30b is protruded by the protrusions 11b and 14b and further protruded by the protrusion 14b, the contact area between the objective lens 30b and the mold 10b is stepwise. Therefore, the objective lens 30b can be released more easily, and the deformation of the objective lens 30b or the damage to the optical function surface at the time of release can be more effectively prevented.

(Third embodiment)
The present embodiment will be described with reference to FIGS. FIG. 11 is a view showing a cross section of the objective lens 30c emitted to the molds 10c and 20c, and FIG. 12 is a view showing a cross section of the objective lens 30c from which the molds 10c and 20c are released. 13 is a diagram showing an incident surface 31c of the objective lens 30c.

  In the apparatus of the present embodiment, as shown in FIG. 11, the mold 10c is provided with a protruding portion 11c, an incident surface forming portion 12c, and a flange forming portion 13c, as in the first embodiment. A gate 14c (injection hole) that is an inlet for molten resin is provided at a substantially central portion of the entrance surface 31c of the objective lens 30c (a position corresponding to the optical axis of the optical function surface of the objective lens 30c). Similarly to the first embodiment, the mold 20c is provided with an emission surface forming portion 21c and a flange forming portion 22c. Further, grooves C1 and C2 are provided between the molds 10c and 20c. As in the first embodiment, the objective lens 30c is provided with an incident surface 31c, an exit surface 32c, and a flange 33c. The cavity C3 is formed by the incident surface forming portion 12c, the exit surface forming portion 21c, and the flange forming portions 13c and 22c.

  Although not shown, the gate 14c is connected to a runner which is a molten resin introduction path. The runner is connected to a sprue through the molten resin, and an injection device for injecting the molten resin is connected to the sprue. ing.

  Next, a method for manufacturing the objective lens 30b by injection molding in the present embodiment will be described. First, as shown in FIG. 11, the gates 14c and the cavity C3 are formed by combining the molds 10c and 20c.

  And molten resin is inject | emitted from an injection apparatus through the sprue which is not shown in figure. The injected molten resin is injected into the cavity C3 through a runner (not shown) and a gate 14c in order. The air remaining in the cavity C3 is exhausted from the grooves C1 and C2 between the molds 10c and 20c.

  Since the gate 14c is located substantially at the center of the incident surface forming portion 12c, as shown in FIG. 13, the molten resin is injected radially from the center of the objective lens 30c into the cavity C3 and solidifies by cooling. Therefore, the occurrence of coma and astigmatism due to the deviation of the transfer speed and contraction speed of the molten resin is prevented, and the objective lens 30c that is axisymmetrically uniform with the central portion 34c as the center (centered on the optical axis) is formed. Then, an optical functional surface is formed on the incident surface 31c by the incident surface forming portion 12c.

  Then, after the molten resin injected into the molds 10c and 20c is solidified by cooling and the objective lens 30c is molded, the mold release process is started. First, the mold 10c is moved to release the mold 20c from the solidified objective lens 30c. As a result, the emission surface 32c and the emission surface side flange 33c are released. And the resin part currently shape | molded by the runner etc. which is not shown in figure is cut | disconnected. As a result, the runner side fixing of the central portion 34c on the incident surface side is released. And the protrusion part 11c is protruded from the metal mold | die 10c, and the flange 33c by the side of an incident surface is released.

  Then, as shown in FIG. 12, the rod-shaped central portion 34c protrudes toward the objective lens 30c, and the incident surface 31c is released. Although the entrance surface forming portion 12c is deep and the contact area with the entrance surface 31c is large, the objective lens 30c can be easily released. Finally, the central portion 34c is cut at a predetermined cutting portion C4. It is preferable to make the cut portion C4 a part away from the incident surface 31c to some extent because the possibility of damaging the incident surface 31c during the cutting is reduced.

  Since no optical functional surface is formed in the central portion 34c, the cross-sectional area of the gate 14c is equal to that of the entrance pupil of the laser light from the laser light source of the optical pickup device as described in the first and second embodiments. Based on the area, the cross-sectional area ratio of the gate 14c may be set to about 16% or less. However, the smaller the cross-sectional area of the gate 14c, the lower the injection efficiency of the molten resin and the longer it takes to inject the molten resin. Further, the larger the cross-sectional area of the gate 14c, the more unnecessary resin parts are formed on the gate 14c, and the more resin is wasted. Considering these points, it is preferable to set the cross-sectional area of the gate 14c to an appropriate value.

  Therefore, according to the present embodiment, the gate 14c for injecting the molten resin is provided at the substantially central portion (position corresponding to the optical axis) of the incident surface forming portion 12c, and the molten resin is injected from the gate 14c into the cavity C3. Therefore, the objective lens 30c which is symmetrically transferred and contracted with respect to the optical axis of the incident surface 31c and is uniformly transferred and contracted is formed, and the occurrence of coma or astigmatism when the objective lens 30c is used is prevented, and injection molding is performed. The optical function of the objective lens 30c can be prevented from being lowered. Similarly to the first embodiment, molten resin is injected into the cavity C3, the molded objective lens 30c is released from the mold 20d, and the objective lens 30c is projected by the projecting portion 11c to mold the mold 10c. Can be easily released to prevent deformation of the objective lens 30c or damage to the optical function unit.

  In the present embodiment, when the objective lens 30c is released, the central portion 34c is protruded from the objective lens 30c from which the mold 20c has been released to release it at once, but this is not restrictive. The objective lens 30c from which the mold 20c has been released is first protruded from the protruding portion 11c, the flange 33c is released, the central portion 34c is protruded from the objective lens 30c remaining on the protruding portion 11c, and the incident surface 31c is released. May be. In this case, since the contact area between the objective lens 30c and the mold 10c is reduced stepwise, the objective lens 30b can be released more easily, and the objective lens 30b is deformed at the time of release or the optical function surface is damaged. Can be more effectively prevented.

(Fourth embodiment)
This embodiment will be described with reference to FIGS. FIG. 14 is a diagram illustrating a cross section of the objective lens 30d emitted to the molds 10d and 20d, and FIG. 15 is a diagram illustrating a cross section of the objective lens 30d from which the molds 10d1, 10d2, and 20d are released. FIG. 16 is a diagram showing an incident surface 31d of the objective lens 30d.

  In the apparatus according to the present embodiment, as shown in FIG. 14, the mold 10d can be divided up and down inside the divided portions 101 and 102, and the divided portions 10d1 and 10d2 that can be divided vertically in FIG. Dividers 11d1 and 11d2 are provided. Similarly to the first embodiment, the split portions 11d1 and 11d2 are provided with an incident surface forming portion 12d, and the split portions 10d1 and 10d2 are provided with a flange forming portion 13d. Further, the dividing portions 10d1 and 11d1 and the dividing portions 10d2 and 11d2 are each integrally divided up and down, and grooves 14d are provided at the boundaries of the upper and lower divisions of the dividing portions 10d1, 10d2, 11d1, and 11d2 at the division boundaries. . The groove 14d passes through a substantially central portion of the incident surface 31d of the objective lens 30d (a position corresponding to the optical axis of the optical function surface of the objective lens 30d).

  Similarly to the first embodiment, the mold 20d is provided with an emission surface forming portion 21d and a flange forming portion 22d. A gate D1 and a cavity D3 are formed by the molds 10d and 20d, and a groove D2 is formed between the mold 10d (divided portion 10d1) and the mold 20d. As in the first embodiment, the objective lens 30d is provided with an entrance surface 31d, an exit surface 32d, and a flange 33d, and a boundary line portion 34d is provided at a portion corresponding to the groove 14d. The cavity D3 is formed by the incident surface forming portion 12d, the exit surface forming portion 21d, and the flange forming portions 13d and 22d.

  Next, a method for manufacturing the objective lens 30d by injection molding in the present embodiment will be described. First, as shown in FIG. 14, the molds 10d and 20d are combined to form the gate D1, the groove D2, and the cavity D3.

  And it enters into the process of injecting molten resin from an injection device via the sprue which is not illustrated. The sprue is connected to a runner (not shown), and the injected molten resin is injected into the cavity D3 through the gate D1. The air remaining in the cavity D3 is exhausted from the grooves 14d and D2.

  Then, after the molten resin injected into the molds 10d and 20d is solidified by cooling and the objective lens 30d is molded, the mold release process is started. First, the mold 10d is moved to release the mold 20d from the solidified objective lens 30d. Thereby, the emission surface 32d and the emission surface side flange 33d are released.

  Then, as shown in FIG. 15, the dividing portions 10d1 and 11d1 are moved upward in the drawing, and the dividing portions 10d2 and 11d2 are moved downward in the drawing to divide the mold 10d vertically. This upper and lower division is in a direction perpendicular to the optical axis of the incident surface 31d. By this upper and lower division, the incident surface 31d, the flange 33d on the incident surface side, and the boundary line portion 34d are released at once. Although the entrance surface forming portion 12d is deep and the contact area with the entrance surface 31d is large, the objective lens 30d can be easily released without requiring a strong force.

  Finally, unnecessary molding portions molded in the gate D1 are cut at a position corresponding to the gate D1, for example, to complete the molding of the objective lens 30d.

  As shown in FIG. 16, also in the injection molding method of the present embodiment, an optical function surface is formed on the incident surface 3d by the incident surface forming portion 12d, and an optical line is formed on the boundary line portion 34d on the incident side of the objective lens 30d. Since the functional surface is not formed, the width of the groove 14d is preferably a thin line of about 0.01 to 0.02 [mm], for example. In this case, the boundary line portion 34d, which is a region where the optical functional surface is not formed, is narrowed to reduce the influence that contributes to the decrease in the optical function of the objective lens 30d, and the air in the cavity D3 is released into the groove 14d. It is possible to prevent the molten resin from entering the groove 14d during the injection molding while taking care.

  Therefore, according to the present embodiment, the molten resin is injected into the cavity D3, the air in the cavity D3 is deaerated into the groove 14d, and the air remains in the objective lens 30d to be molded, and the optical function of the objective lens 30d. The objective lens 3d is released from the mold 20d, and the mold 10d is divided in the direction perpendicular to the optical axis with the line perpendicular to the optical axis of the objective lens 30d as a boundary. Since the lens 30d is released, the mold 10d can be easily released from the objective lens 30d, the deformation of the objective lens 30d or damage to the optical function surface is prevented, and the optical function of the objective lens 30d is lowered during injection molding. Can be prevented.

  In addition, in this Embodiment, although it was the structure which provided two division parts (10d1, 11d1) and (10d2, 11d2) on each upper and lower sides about the metal mold | die 10d, the division parts 10d1 and 11d1 are formed integrally, The structure which forms the division parts 10d2 and 11d2 integrally may be sufficient. Further, the present invention is not limited to the configuration in which the upper and lower parts are divided, and the mold is divided into two or more divided parts in the direction perpendicular to the optical axis with the line passing through the optical axis of the incident surface 30d as a boundary. Good.

  In the first to fourth embodiments, resin such as plastic is used as the material of the objective lens. However, the present invention is not limited to this, and other melting materials such as low-melting glass may be used. In the first to fourth embodiments, the objective lens 30a, 30b, 30c, 30d having an image-side aperture ratio of 0.8 is manufactured, and the image-side aperture ratio is 0.8 or more. Each embodiment may be applied to manufacture a lens having an image-side aperture ratio of less than 0.8.

  In the first to fourth embodiments, the objective lens for the optical pickup device has been described as the optical element. However, the present invention is not limited to this, but a collimator, a cylindrical lens, a reflection mirror, a half mirror, a beam splitter, and the like. It can be applied to other optical elements. Further, the present invention can also be applied to optical elements such as lenses used in other devices such as cameras.

  In the first to fourth embodiments, the configuration for preventing the optical function from being deteriorated on the incident surface of the laser beam has been described. However, the present invention is not limited to this, and either one or both of the incident surface and the exit surface. It is good also as a structure which prevents the fall of the optical function. For example, in the first embodiment, a deaeration hole may be provided in a substantially central portion (a position corresponding to the optical axis) of either one or both of the incident surface forming portion and the emitting surface forming portion. In the embodiment, the protruding portion may be provided at substantially the central portion (position corresponding to the optical axis) of either one of the incident surface forming portion and the emitting surface forming portion. In the third embodiment, the incident surface forming portion is formed. A gate may be provided at substantially the center part (position corresponding to the optical axis) of either one or both of the light emitting portion and the light exit surface forming portion. In the fourth embodiment, the entrance surface forming portion and the light exit surface forming portion A configuration may be employed in which the mold is divided in a direction perpendicular to the optical axis with a line passing through one or both optical axes as a boundary. Furthermore, the structure which combines at least 2 or more of the 1st-4th embodiment may be sufficient.

  In the first to third embodiments, the deaeration hole 14a, the protruding portion 14b, and the gate 14c are respectively placed on the optical axes of the optical function surfaces of the objective lenses 30a, 30b, and 30c in the molds 10a, 10b, and 10c. Although it is provided at a corresponding position, a configuration in which the objective lens 30a, 30b, 30c is provided in the vicinity of a position corresponding to the optical axis of the optical function surface is also conceivable. Similarly, in the fourth embodiment, the groove 14d is provided so as to pass through a position corresponding to the optical axis of the optical function surface of the objective lens 30d, but corresponds to the optical axis of the optical function surface of the objective lens 30d. A configuration provided near the position to be considered is also conceivable.

  As mentioned above, although embodiment and this invention were demonstrated, this invention is not necessarily limited only to the means and method mentioned above, The range which achieves the objective said to this invention and has the effect said to this invention It is possible to make changes as appropriate.

It is a figure which shows the cross section of metal mold | die 10a, 20a. It is a figure which shows the cross section of the objective lens 30a inject | emitted by metal mold | die 10a, 20a. It is a figure which shows the cross section of the objective lens 30a from which the metal mold | die 20a was released. It is a figure which shows the cross section of the objective lens 30a protruded by the protrusion part 11a. It is a figure which shows the entrance plane 31a of the objective lens 30a. It is a figure which shows the cross section of the objective lens 30b inject | emitted by metal mold | die 10b, 20b. It is a figure which shows the cross section of the objective lens 30b from which the metal mold | die 20b was released and protruded to the protrusion parts 11b and 14b. It is a figure which shows the cross section of the objective lens 30b protruded by the protrusion part 14b, after the metal mold | die 20b was released and protruded by the protrusion parts 11b and 14b. It is a figure which shows the cross section of the objective lens 30b from which the metal mold | die 20b was released and protruded to the protrusion part 14b. It is a figure which shows the entrance plane 31b of the objective lens 30b. It is a figure which shows the cross section of the objective lens 30c inject | emitted by the metal mold | die 10c, 20c. It is a figure which shows the cross section of the objective lens 30c from which the metal mold | dies 10c and 20c were released. It is a figure which shows the entrance plane 31c of the objective lens 30c. It is a figure which shows the cross section of the objective lens 30d inject | emitted by the metal mold | dies 10d and 20d. It is a figure which shows the cross section of 30d of objective lenses from which metal mold | die 10d1, 10d2, 20d was released. It is a figure which shows the entrance plane 31d of the objective lens 30d. It is a figure explaining shaping | molding of the conventional objective lens.

Explanation of symbols

10a, 10b, 10c, 10d ... molds 11a, 11b, 14b, 11c, 11d ... projecting portions 12a, 12b, 12c, 12d ... incident surface forming portions 13a, 13b, 13c, 13d ... flange forming portions 14a ... deaeration holes 14c ... Gate 14d ... Groove 15b ... Projection surfaces 20a, 20b, 20c, 20d ... Molds 21a, 21b, 21c, 21d ... Emission surface forming portions 22a, 22b, 22c, 22d ... Flange forming portions 30a, 30b, 30c, 30d ... objective lenses 31a, 31b, 31c, 31d ... entrance surfaces 32a, 32b, 32c, 32d ... exit surfaces 33a, 33b, 33c, 33d ... flanges 34a, 34b, 34c, 34d ... center portions A1, B1 ... runners A2, B2 D1, gates A3, B3, C3, D3 ... cavities C1, C2, B4, D2 ... grooves C4 ... cut Part 40 ... Mold 41 ... Projection part 42 ... Incident surface forming part 43 ... Flange forming part 44 ... Central part 50 ... Mold 51 ... Outgoing surface forming part 52 ... Flange forming part 60 ... Objective lens 61 ... Incident surface 62 ... Outgoing Surface 63 ... Flange E1 ... Runner E2 ... Gate E3 ... Cavity E4 ... Groove

Claims (10)

In an objective lens manufacturing method for manufacturing an objective lens for an optical pickup device having an optical function unit by injecting a molten material into a mold,
The mold has a function of forming the optical function part on the objective lens, and when the mold is opened, the mold is formed when the mold is opened with the first mold part where the molded objective lens remains. A second mold part from which the objective lens is released,
The first mold part includes a first protrusion part that protrudes an objective lens, and the first protrusion part is provided at a position corresponding to an optical axis of an optical function part of the objective lens, and And having a cross-sectional area of 16% or less with respect to the area of the entrance surface of the objective lens in contact with the mold part or the area of the exit surface of the objective lens in contact with the first mold part,
Injecting the molten material into the mold, releasing the second mold part from the molded objective lens, and opening the mold,
An objective lens manufacturing method, wherein the objective lens from which the second mold part has been released is protruded by the first protrusion part, and the first mold part is released from the objective lens. The first mold part has a function of forming the optical function part in the objective lens, and includes a second protrusion part that protrudes the objective lens from which the second mold part is released,
The first mold part is released by projecting the objective lens from which the second mold part has been released by the first and second projecting parts, and the objective remaining in the second projecting part. The objective lens manufacturing method according to claim 1, wherein the lens is further protruded by the first protrusion and the first mold part is released.   The objective lens manufacturing method according to claim 1, wherein the first protrusion includes an optical function forming unit that forms an optical function unit of the objective lens.   The objective lens manufacturing method according to claim 1, wherein the objective lens has an annular diffraction structure.   The objective lens manufacturing method according to claim 4, wherein the annular diffractive structure is formed by the first mold part. In an objective lens manufacturing mold that molds and manufactures an objective lens for an optical pickup device that has an optical function part by injection of a molten material,
A first mold part that has a function of forming an optical function part of the objective lens and in which the molded objective lens remains in the state when the mold is opened;
A second mold part from which the molded objective lens is released when the mold is opened;
The first mold part includes a first protrusion part that protrudes an objective lens from which the second mold part is released when the mold is opened, and the first protrusion part is the optical function part. The area of the entrance surface of the objective lens in contact with the first mold part or the area of the exit surface of the objective lens in contact with the first mold part is provided at a position corresponding to the optical axis of An objective lens manufacturing mold having a cross-sectional area of 16% or less. The first mold part has a function of forming the optical function part in the objective lens, and a second projecting part that projects the objective lens from which the second mold part has been released when the mold is opened. With
The objective lens manufacturing mold according to claim 6, wherein the first protruding portion further protrudes the objective lens left in the second protruding portion.   8. The objective lens manufacturing mold according to claim 6, wherein the first protrusion includes an optical function forming unit that forms an optical function unit of the objective lens.   The mold for manufacturing an objective lens according to any one of claims 6 to 8, wherein the objective lens has an annular diffraction structure.   The mold for manufacturing an objective lens according to claim 9, wherein the annular diffractive structure is formed by the first mold part.

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