JP4407148B2 - Optical element manufacturing method and apparatus, and optical element - Google Patents

Description

[0001]
[Field of the Invention]
The present invention relates to a method for manufacturing a plastic optical element having a fine pattern such as a diffraction pattern.
[0002]
[Prior art]
As a plastic diffractive lens manufacturing apparatus, a mold surface corresponding to the diffractive structure is provided on the movable mold side where the diffractive lens as a molded product remains in the mold open state, and the diffractive lens is released from the movable mold. Some of them have a protruding mechanism. In such a manufacturing apparatus, the end surface of the protrusion mechanism is a mold surface corresponding to the diffractive structure of the diffractive lens, that is, the optical surface itself. Thereby, when releasing a diffraction lens from this movable metal mold | die, a molded product is reliably extruded through the part of the diffraction structure (for example, refer patent document 1, 2).
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-200652
[Patent Document 2]
Japanese Patent Laid-Open No. 2002-200654
[Problems to be solved by the invention]
However, in the manufacturing apparatus as described above, (1) when the mold is opened, the molded product may be minutely released (about 1 μm) in the movable side mold. In this state, the molded product cools and contracts, and a phenomenon occurs in which the edge of the molded product interferes with the diffraction edge of the mold and deforms.
[0004]
(2) Furthermore, a phenomenon occurs in which the diffraction edge is deformed by extruding and releasing the molded product while the diffraction edge of the molded product is shifted from the diffraction edge of the mold.
[0005]
Due to the above phenomena (1) and (2), the diffractive edge of the molded product may be abnormally deformed on the order of several μm to deteriorate the optical performance of the diffractive lens.
[0006]
Accordingly, the present invention provides a method and apparatus for manufacturing an optical element in which a shape defect such as a diffractive structure of a molded product is unlikely to occur during mold opening and release, and an optical element manufactured by such a method. Objective.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, a method of manufacturing an optical element according to the present invention includes a step of filling a resin in a cavity formed by a first mold member and a second mold member facing the first mold member; A step of opening the mold by separating the first mold member relative to the second mold member at a stage where the resin in the cavity is solidified to a predetermined level or more; and after the mold opening process, A step of releasing a molded product obtained from the resin in the cavity from the optical surface of the first mold member by projecting a protruding member provided avoiding the optical surface on the type 1 member side; Holding the molded product in a state of being close to the first mold member.
[0008]
In the above manufacturing method, since the protruding member for releasing the molded product from the optical surface of the first mold member is provided on the first mold member side avoiding the optical surface, the optical surface of the molded product is separated. It can be prevented from being damaged by the mold. That is, since the optical surface of the molded product and the protruding member are not in direct contact with each other at the time of mold release, it can be avoided that the optical surface of the molded product reshapes with the protruding member, and the optical characteristics of the molded product deteriorate. Can be prevented. In addition, since the released molded product is once held in the state of being close to the first mold member, a sprue or the like extending from the molded product can be reliably chucked at a desired timing after the mold release. Therefore, it is possible to easily and surely prevent the molded product from dropping at the time of releasing by the protruding member. Thereafter, in the normal case, after additional mold opening is performed, additional mold release is performed.
[0009]
The distance for separating the first and second mold members in the mold opening process needs to have a certain width or more so that the molded product can be reliably released from the first mold member. Since the time until release becomes longer, the amount of shrinkage of the molded product increases, so it is desirable to set this distance small so as to reduce deformation due to shrinkage of the molded product.
[0010]
Moreover, in the specific aspect of the said manufacturing method, the fine pattern is provided in the optical surface of the said 1st type | mold member. Here, the “fine pattern” means a pattern including a local concavo-convex shape. In addition to the optical path difference providing structure such as a diffraction pattern and a phase difference formation pattern, two-dimensional illumination is performed using a step. A light guide plate and the like are also included. The diffraction pattern refers to a form in which a relief is provided on the surface of an optical element, for example, a lens surface, and has an effect of changing the angle of light rays by diffraction, and the phase difference formation pattern is an optical element surface, for example, a lens surface. Is a form in which a stepped shape is provided to provide a phase difference to the light beam. According to the above manufacturing method, the fine pattern formed on the molded product can be prevented from being damaged by the mold release, and the optical characteristics to be achieved by the diffraction structure of the molded product can be prevented from being deteriorated. When a fine pattern is provided on the optical surface, it is desirable that the time until the protruding member is protruded after the mold opening process is short, but a delay time that does not cause significant shrinkage of the molded product is allowed.
[0011]
Moreover, in another specific aspect of the manufacturing method, the protrusion amount of the protrusion member when releasing the molded product from the optical surface of the first mold member is equal to or greater than the unevenness amount of the fine pattern. In this case, even if the molded product shrinks after the mold release, it is possible to reliably avoid re-contact of the fine pattern portion of the molded product and the optical surface of the first mold member.
[0012]
In still another specific aspect of the manufacturing method, the released molded product is held in proximity to the first mold member in a state of being shallowly fitted to the first mold member. In this case, the first mold member itself can be used to easily prevent the dropout before the molded product is taken out after being released.
[0013]
Further, in still another specific aspect of the manufacturing method, the protruding amount of the protruding member when the molded product is released from the optical surface of the first mold member is determined on the molding surface of the first mold member. It is smaller than the maximum length with respect to the protruding direction of a portion that extends uniformly or continuously in the protruding direction of the protruding member. In this case, detachment of the molded product can be prevented using the molding surface formed on the first mold member itself. Note that “a portion extending uniformly or continuously in the protruding direction” corresponds to a cylindrical side surface of the outer peripheral flange portion or the like when the molded product is a diffractive lens, for example.
[0014]
Further, in still another specific aspect of the manufacturing method, after the releasing step or during the step, the step of further separating the first mold member from the second mold member and performing additional mold opening is further performed. Prepare. In this case, since the mold opening is performed in two stages, it is possible to prevent re-contact with the mold when the molded product rapidly cools and shrinks by the first mold opening and protrusion, and preparation for taking out the molded product by additional mold opening is possible.
[0015]
According to still another specific aspect of the above manufacturing method, after the additional mold opening step, the protruding member is further protruded to further separate the molded product from the optical surface of the first mold member. The method further includes a step of performing additional release. In this case, the molded product can be separated from the first mold member and taken out to the outside.
[0016]
According to still another specific aspect of the manufacturing method, the molded product that has been initially released is held in proximity in a state of being separated from the first mold member by the support of the protruding member. In this case, the dropping member can be easily prevented from dropping before the molded product is taken out after being released.
[0017]
Further, in still another specific aspect of the manufacturing method, the mold opening distance in the initial mold opening process is such that the protruding member protrudes when the molded product is released from the optical surface of the first mold member. Greater than quantity. In this case, it is possible to prevent a molding defect from occurring when the molded product hits the second mold member due to mold release.
[0018]
In still another specific aspect of the manufacturing method, the first mold member is a movable mold, and the second mold member is a fixed mold. In this case, the molded product remains on the movable mold side, that is, the released molded product is held in a state of being close to the first mold member.
[0019]
The optical element manufacturing apparatus according to the present invention includes a first mold member provided with an optical surface having a fine pattern, a second mold member disposed to face the first mold member, the first and the second mold members, Resin supply means for filling the resin formed in the cavity formed by the second mold member, and a projecting member provided on the first mold member side so as to avoid the optical surface and capable of projecting on the inner surface side of the first mold member An opening / closing mechanism that relatively opens and closes the first and second mold members, an advance / retreat mechanism that operates the protruding member, and the opening / closing mechanism operates when the resin in the cavity is solidified to a predetermined level or more. And opening the mold by separating the first mold member relative to the second mold member and operating the advance / retreat mechanism to project the protruding member after the mold opening. In the cavity The molded article obtained from the fat is released from the optical surface of the first mold member, and a control unit for temporarily be held in a state where a release has been the molded article proximate to the first mold member.
[0020]
In the manufacturing apparatus, the control device operates the advance / retreat mechanism after the initial mold opening process to project the protruding member provided avoiding the optical surface, thereby releasing the molded product from the optical surface of the first mold member. Therefore, when the molded product is released from the first mold member, the optical surface of the molded product does not directly contact the protruding mechanism. Therefore, it can be avoided that the optical surface of the molded product becomes defective due to re-contact, and the optical characteristics of the molded product can be prevented from deteriorating. In addition, since the molded product that has been initially released is temporarily held in the state of being close to the first mold member, a sprue or the like extending from the molded product can be reliably chucked at a desired timing after release. Therefore, it is possible to easily and surely prevent the molded product from dropping at the time of releasing by the protruding member.
[0021]
An optical element according to the present invention is formed by the method for manufacturing an optical element according to any one of claims 1 to 10. In this case, as is apparent from the above description, it is possible to provide an optical element having good optical characteristics such as a diffractive lens having almost no shape defect on the optical surface.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
[First Embodiment]
FIG. 1 is a block diagram conceptually illustrating the structure of the optical element manufacturing apparatus according to the first embodiment.
[0023]
This manufacturing apparatus includes a fixed mold 12, a movable mold 14, a temperature adjustment unit 22, a movable drive unit 24, a pin drive unit 26, a resin injection unit 28, and a control device for comprehensive control of these. 32.
[0024]
FIG. 2 is a longitudinal sectional view for explaining the shapes and structures of the fixed mold 12 and the movable mold 14, and FIG. 3 is a front view for explaining the arrangement of the projecting pins 16 that are projecting members provided on the movable mold 14. .
[0025]
As is clear from the figure, the fixed mold 12 has a smooth concave optical surface 12 a facing the movable mold 14. The optical surface 12a corresponds to one lens surface of a plastic lens that is a molded product.
[0026]
On the other hand, the movable mold 14 has an optical surface 14a which is provided with a diffraction pattern DP facing the fixed mold 12 and is concave as a whole, and has an annular groove 14b around the optical surface 14a. ing. The optical surface 14a corresponds to the other lens surface of the plastic lens that is a molded product, and the groove 14b corresponds to a flange around the plastic lens. The protruding pins 16 are arranged at equal intervals in four locations of an annular groove 14b provided in the movable die 14. When the protruding pin 16 is in the retracted position, as shown in FIG. 2, the tip 16a of the protruding pin 16 has substantially the same height as the bottom of the groove 14b. When the protrusion pin 16 is in the operating position, the tip 16a of the protrusion pin 16 is in a state of protruding from the bottom of the groove 14b. The distance for releasing the molded product can be adjusted in two stages depending on the protruding amount of the ejector pin 16, and will be described in detail below. In the initial release in the previous stage, the molded product is removed by the initial release distance by the groove 14b. The mold is released from the bottom, and in the subsequent additional release, the molded product is released from the bottom of the groove 14b by an additional release distance.
[0027]
FIG. 4 is a front view showing a modification of the protruding pin 16 shown in FIG. 3, and a cylindrical protruding sleeve 216 is provided between the central portion 214 a and the peripheral portion 214 b of the movable mold 24. In this case, while keeping the relative positions of the central portion 214a and the peripheral portion 214b, the sleeve 216 is protruded stepwise with respect to them so that the molded product can be moved by the initial release distance or the additional release distance. That is, the mold can be released from the central portion 214a and the peripheral portion 214b.
[0028]
Returning to FIG. 1, the temperature adjustment unit 22 includes a heater and its control circuit, and adjusts the temperatures of the fixed mold 12 and the movable mold 14 during molding. Thereby, the molten plastic material introduced into the cavity formed by the fixed mold 12 and the movable mold 14 can be cooled at a desired speed from the fixed mold 12 and the movable mold 14 side.
[0029]
The movable drive unit 24 is an opening / closing mechanism including a drive device such as a motor, and can move the movable mold 14 in close contact with the fixed mold 12 or be separated by a desired distance. As a result, when forming with both molds 12 and 14, the cavity formation timing, the initial mold opening timing after molding, and the like are set to desired conditions. The distance between the fixed mold 12 and the movable mold 14 can be adjusted in two stages. In the first state where the distance is narrow, the movable mold 14 is separated from the fixed mold 12 by the initial mold opening distance, and the distance between the fixed mold 12 and the movable mold 14 is wide. In the second state, the movable mold 14 is separated from the fixed mold 12 by an additional mold opening distance.
[0030]
The pin driving unit 26 is an advancing / retracting mechanism including a driving device such as a motor, and the four protruding pins 16 provided on the movable mold 14 can be advanced / retreated in two stages in synchronization with each other at an appropriate timing. That is, the tip 16a of each protruding pin 16 is driven by the pin driving unit 26 and retracted to the molding surface 14b of the movable mold 14, and a minute amount from the molding surface 14b (that is, the above-described initial release distance). It reciprocates at an appropriate timing between the first protrusion position protruding only and the second protrusion position protruding substantially to the end face of the movable die 14 (that is, the above-mentioned additional release distance). When the protruding pin 16 is in the retracted position, the tip 16a does not need to be exactly coincident with the molding surface 14b, and can be in a state of being retracted, for example, about several mm behind the molding surface 14b. In this case, even if the protrusion pin 16 moves to the first protrusion position, the tip 16a may not protrude from the molding surface 14b.
[0031]
The resin injection part 28 is a resin supply means, and supplies a molten plastic material via a runner or a gate (not shown) into a cavity formed when the fixed mold 12 and the movable mold 14 are fixed to each other. Fill the cavity with molten plastic material. The molten plastic material is appropriately selected according to the characteristics required for the diffractive plastic lens to be molded.
[0032]
The control device 32 is configured by a computer or the like, and comprehensively controls the operations of the movable drive unit 24, the pin drive unit 26, and the resin injection unit 28 based on a program input in advance. Thereby, as will be described in detail below, a series of operations such as mold matching, material injection, initial mold opening, initial mold release, and additional mold release can be performed under desired conditions and timing.
[0033]
FIG. 5 is a flowchart for explaining an outline of the operation of the apparatus shown in FIG. First, the movable mold drive unit 24 is operated to move the movable mold 14 toward the fixed mold 12, and the mold is closed by joining the movable mold 14 to the fixed mold 12 (step S1). At this time, the fixed mold 12 and the movable mold 14 are fixed in a state where they are aligned with each other using alignment means such as a fitting pin (not shown). By such mold closing, a cavity having a shape in which the optical surface 12 a of the fixed mold 12 and the optical surface 14 a of the movable mold 14 are closed is formed between both molds 12 and 14.
[0034]
Next, the resin injection unit 28 is operated to inject the molten plastic resin into the cavity formed between both molds 12 and 14 (step S2). The molten plastic resin supplied from the resin injection unit 28 is introduced into the cavity between the molds 12 and 14 via a runner and a gate (not shown) to fill the cavity.
[0035]
FIG. 6A is a cross-sectional view showing a state immediately after the molten plastic resin MP is filled in step S2. The fixed mold 12 and the movable mold 14 are joined to each other, and the cavity formed between them is completely filled with the molten plastic resin. That is, the molten plastic resin MP filled in the cavity flows or deforms so as to conform to the diffraction pattern DP constituting the optical surface 14a provided on the movable mold 14, and embeds minute grooves in the diffraction pattern DP.
[0036]
Returning to the flowchart of FIG. 5, the molten plastic resin MP filled in the cavity is then radiated and cooled while appropriately controlling the temperatures of the fixed mold 12 and the movable mold 14 (step S3). At this time, the temperature setting of both molds 12 and 14 and the holding time of the molten plastic resin MP, that is, the cooling rate and cooling time are appropriately set in consideration of the type of the molten plastic resin MP, the capacity of the cavity, and the like.
[0037]
Next, the movable mold driving unit 24 is operated to perform initial mold opening that slightly separates the movable mold 14 from the fixed mold 12 (step S4). That is, the movable mold 14 is in the first state separated from the fixed mold 12 by the initial mold opening distance that is a relatively small distance. As a result, the molded product remains on the movable mold 14 side and is released from the fixed mold 12. Here, the initial mold opening distance is such as to enable the initial mold release performed below, and is not so large. This prevents the molded product from being deformed by the mold (that is, the pattern DP) due to cooling shrinkage while preventing the molded product from hitting the fixed mold 12 due to the initial mold release, which will be described below. . If the initial mold opening distance becomes too large, the molded product cools and contracts during the initial mold opening. Therefore, depending on the degree of the initial mold release, the movable mold 14 has a fine diffraction pattern formed on the molded product. The minute diffraction pattern DP provided bites in and tends to cause poor formation.
[0038]
Following this initial mold opening or in parallel with the initial mold opening, the pin driving section 26 is operated to move the four protruding pins 16 into the retracted position where the tips 16a are housed in the bottom of the groove 14b of the movable mold 14. The tip 16a is moved to the first protrusion position where the tip 16a protrudes by the initial release distance (step S5). This initial mold release not only prevents the formation of defective molding in the diffraction pattern of the molded product, but also enables easy chucking of the molded product in the next process while preventing the molded product from falling off the movable mold 14. Become. In the case where the initial mold opening and the initial mold release are performed in parallel, it is possible to prevent the molded product from hitting the fixed mold 12 due to the initial mold release, for example, by slowing the protruding speed of the ejecting pin 16 to cause a molding defect. On the other hand, when the initial mold release is started after a certain waiting period after the opening of the initial mold is completed, the waiting time should not be so long. This is to prevent the molded product from contracting before the initial mold release and the diffraction pattern thereof to be deformed by the diffraction pattern DP of the movable mold 14. The waiting time needs to be adjusted as appropriate according to the cooling rate of the molded product.
[0039]
FIG. 6B is a cross-sectional view showing a state where the molded product is initially released from the movable mold 14 in step S5. The plastic lens PL, which is a molded product fitted into the optical surface 14a of the movable die 14, is initially separated slightly from the optical surface 14a as a result of the peripheral flange portion PLa being pushed outward by the protruding pin 16. The mold is released. In this way, the plastic lens PL is initially released from the movable mold 14 immediately after the initial mold opening, so that the diffraction formed in the plastic lens PL can be obtained even when the plastic lens PL is cooled and contracted after that. Contact or interference between the lens surface PLb and the diffraction pattern formed on the optical surface 14a of the movable mold 14 can be completely avoided.
[0040]
Here, the initial mold release distance La at which the plastic lens PL is initially released from the movable mold 14 is Lb when the depth of the diffraction pattern formed on the optical surface 14a of the movable mold 14 is Lb (FIG. 6D). See below) and satisfy the following relationship:
[Expression 1]
Lb <La (1)
In this case, even if the plastic lens PL is cooled and contracted after the initial mold opening, the optical surface 14a and the diffractive lens surface PLb can be prevented from interfering with each other. The characteristic deterioration of the diffractive lens surface PLb can be prevented. In a specific example, since the depth Lb of the diffraction pattern is several μm, the initial release distance La is set to about 10 μm.
[0041]
The initial mold release distance La satisfies the following relationship, where the depth of the groove 14b of the movable mold 14 is Lc.
[Expression 2]
La <Lc (2)
That is, the depth Lc of the groove 14b is Movable type 14 If the condition (1) is satisfied, the maximum depth of the local recesses and the like formed in the region (that is, the maximum length with respect to the protruding direction of the member extending in the protruding direction). It is possible to prevent the plastic lens PL from falling off. In a specific embodiment, the depth Lc of the groove 14b of the movable mold 14 is about 1 mm.
[0042]
Returning to the flowchart of FIG. 5, next, the movable mold drive unit 24 is operated to perform additional mold opening for further separating the movable mold 14 from the fixed mold 12 (step S6). That is, the movable die 14 is in the second state separated from the fixed die 12 by an additional die opening distance that is a relatively large distance. Here, the additional mold opening distance is such that additional plastic mold PL removal and removal from the mold can be performed as described below, and is greater than or equal to the thickness of the plastic lens PL.
[0043]
Next, the plastic lens PL is chucked (step S7). Since a sprue (not shown) extends from the plastic lens PL through a gate portion or the like, the sprue is held by a chuck device (not shown). Thereby, it is possible to prevent the plastic lens PL from dropping from the movable mold 14 in the subsequent additional mold releasing step.
[0044]
Next, the pin driving unit 26 is operated with an appropriate waiting time, and each protrusion pin 16 is added from the first protrusion position where the tip 16a protrudes by the initial release distance La (that is, the initial protrusion position). It moves to the 2nd protrusion position (namely, additional protrusion position) protruded only by mold release distance Ld (step S8).
[0045]
FIG. 6C is a cross-sectional view illustrating a state in which the plastic lens PL is additionally released from the movable mold 14 in step S8. As a result of the plastic lens PL as a molded product being pushed outward by the pin 16 by an additional release distance Ld, Movable type 14 It is in a state completely separated from. Thereby, the plastic lens PL can be taken out between the fixed mold 12 and the movable mold 14. The plastic lens PL is chucked in the previous step S7 and does not fall. In a specific example, the additional release distance Ld is about 2 mm.
[0046]
Finally, the flange portion PLa on the outer periphery of the plastic lens PL is held, and a gate portion (not shown) extending from the flange portion PLa is cut to complete the plastic lens PL (step S9).
[0047]
FIGS. 7A to 7D are reference views for explaining the cause of molding defects on the diffractive lens surface PLb formed on the plastic lens PL for comparison. FIG. 7A is an enlarged cross-sectional view showing the relationship between the movable mold 114 and the plastic lens PL before the mold is opened. FIG. 7B is an enlarged cross-sectional view showing the relationship between the movable mold 114 and the plastic lens PL immediately after the mold opening. The movable mold 114 and the plastic lens PL are considered to be separated by about 1 μm or more due to the influence of mold opening. FIG.7 (c) is a figure explaining the comparative example which did not perform the initial mold release process immediately after mold opening. The movable mold 114 bites into the protruding portion of the plastic lens PL contracted in the center direction by cooling, and the pattern transfer is deteriorated. According to the experiment, it was recognized that in the plastic lens PL that was not subjected to the initial mold release process as described above, there was a tendency that the transfer failure was remarkable on the outer periphery of the plastic lens PL. FIG. 7D is a diagram for explaining a comparative example in which the plastic lens PL is projected using the optical surface of the movable die 114. In this case, the movable mold 114 not only bites into the protruding portion PLe of the plastic lens PL, but also deforms the protruding portion PLe so as to be partially rolled up, thereby forming a scratched portion PLf.
[0048]
FIGS. 7E to 7G are diagrams for explaining a case where a molding defect occurs on the diffractive lens surface in a process slightly different from the case of FIGS. 7A to 7D. The state immediately after the mold opening illustrated in FIG. 7E is a separation distance (for example, 3 μm) larger than the separation distance in FIG. In this case, as shown in FIG. 7F, even when the plastic lens PL contracts, the movable die 114 does not bite into the protruding portion PLe of the plastic lens PL. However, when the plastic lens PL is projected using the optical surface of the movable mold 114, the movable mold 114 partially deforms the projection portion PLe of the plastic lens PL as shown in FIG. A scratched part PLf is formed here.
[0049]
FIG. 8 is a diagram schematically showing a configuration of an optical pickup apparatus including an optical system for optical pickup using a plastic lens manufactured by the above manufacturing apparatus and method as an objective lens.
[0050]
This optical pickup device has a semiconductor laser 62 for reproducing information on a first optical disc 61 that is an information recording medium, and a semiconductor laser 66 for reproducing information on a second optical disc 65 that is an information recording medium. Laser beams having different wavelengths can be emitted. The laser beams from both the semiconductor lasers 62 and 66 are applied to the optical discs 61 and 65 using a diffractive objective lens 77 which is a plastic lens PL formed by the method shown in FIGS. The reflected light from the light is collected using this objective lens 77. The thickness of one substrate of the optical disk is 0.6 ± 0.1 mm, and the thickness of the other substrate is 1.2 ± 0.1 mm, which are different from each other.
[0051]
First, when reproducing the first optical disc 61, a beam is emitted from the first semiconductor laser 62, and the emitted light beam is transmitted through the beam splitter 71, and the polarized beam splitter 72, the collimator 73, and the quarter wavelength plate 74 are passed through. The light passes through and becomes a circularly polarized parallel light beam. This light beam is focused by a diaphragm 76 and is condensed by the objective lens 77 on the information recording surface 61b via the transparent substrate 61a of the first optical disk 61.
[0052]
The light beam modulated and reflected by the information bit on the information recording surface 61b is transmitted again through the objective lens 77, the diaphragm 76, the quarter wavelength plate 74, and the collimator 73, enters the polarization beam splitter 72, and is reflected there. Astigmatism is given by the cylindrical lens 78 and incident on the photodetector 79, and a read signal of information recorded on the first optical disc 61 is obtained using the output signal.
[0053]
In addition, focus detection and track detection are performed by detecting a change in the amount of light due to a change in the shape and position of the spot on the photodetector 79. Based on this detection, the two-dimensional actuator 81 moves the objective lens 77 in the optical axis direction so that the light beam from the first semiconductor laser 62 forms an image on the recording surface 61b of the first optical disk 61, and this semiconductor laser. The objective lens 77 is moved in a direction perpendicular to the optical axis so that the light flux from 62 is imaged on a predetermined track.
[0054]
On the other hand, when reproducing the second optical disk 65, a beam is emitted from the second semiconductor laser 66, and the emitted light beam is reflected by the beam splitter 71, which is a light synthesizing unit, and is combined with the light beam from the first semiconductor laser 62. Similarly, the light passes through the polarization beam splitter 72, the collimator 73, the quarter wavelength plate 74, the diaphragm 76, and the objective lens 77, and is condensed on the information recording surface 65b via the transparent substrate 65a of the second optical disk 65.
[0055]
The light beam modulated and reflected by the information bit on the information recording surface 65 b is again passed through the objective lens 77, the aperture 76, the quarter wavelength plate 74, the collimator 73, the polarization beam splitter 72, and the cylindrical lens 78, and the photodetector 79. A signal for reading information recorded on the second optical disk 65 is obtained by using the output information.
[0056]
Further, as in the case of the first optical disc 61, the spot shape change on the photodetector 79 and the light quantity change due to the position change are detected, and focus detection and track detection are performed, and the two-dimensional actuator 81 is used for focusing. The objective lens 77 is moved for tracking.
[0057]
Since this optical pickup apparatus uses an objective lens 77 made of a plastic lens PL (see FIG. 6C, etc.) with less disturbance in shape, light of different wavelengths from the semiconductor lasers 62 and 66 can be obtained with low aberration. It can be focused or imaged.
[0058]
[Second Embodiment]
The optical element manufacturing apparatus according to the second embodiment will be described below. Since the apparatus of the second embodiment is a modification of the apparatus of the second embodiment, the same portions are denoted by the same reference numerals, and only overlapping portions will be described.
[0059]
9A and 9B are cross-sectional views of the movable mold 14 of the manufacturing apparatus according to the second embodiment. In this case, even if the protruding pin 116 is in the retracted position, the tip 116a of the protruding pin 116 is in a state protruding from the bottom of the annular groove 14b provided in the movable die 14 by a predetermined amount (FIG. 9A). )reference). That is, the protruding pin 116 is in a protruding state from the beginning. Further, when the projecting pin 116 moves from the retracted position to the operating position, the tip 116a of the projecting pin 116 is additionally projected from the bottom of the annular groove 14b provided in the movable mold 14 by a collective release distance. (See FIG. 9B). In this way, by projecting the tip 116a of the ejector pin 116, the plastic lens PL as a molded product can be pushed outward by the mold release distance by the ejector pin 116, and the plastic lens PL is ejected once. The mold can be separated from the optical surface 14a by the operation (collective ejection operation). At this time, since the tip 116a of the protruding pin 116 is fitted into the plastic lens PL by the amount corresponding to the initial protrusion, the plastic lens PL can be supported by the protruding pin 116, and the plastic lens PL is dropped by batch release. Can be prevented.
[0060]
FIG. 10 is a flowchart illustrating the manufacturing method according to the second embodiment. Here, the steps up to step S3 are the same as those in the first embodiment, and thus the description thereof is omitted.
[0061]
After the molten plastic resin is radiated and cooled in step S3, initial mold opening for separating the movable mold 14 from the fixed mold 12 is performed (step S14). As a result, the molded product remains on the movable mold 14 side and is released from the fixed mold 12.
[0062]
Next, the protrusion pin 16 is moved from the retracted position to the protrusion position, and the plastic lens PL is completely released from the optical surface 14a (step S15). This collective mold release not only prevents the formation of defective molding in the diffraction pattern of the molded product, but also allows the plastic lens PL to fall off by supporting the protruding pins 16.
[0063]
Next, additional mold opening (step S16) is performed. The mold opening amount in this step is set to such an extent that the molded product PL can be taken out after batch release.
[0064]
Next, the plastic lens PL is chucked (step S17). At this time, the protruding pin 16 is retracted from the protruding position to the retracted position, and the support of the plastic lens PL by the protruding pin 16 is released.
[0065]
Finally, the plastic lens PL is taken out between the two molds 12 and 14, the flange portion PLa on the outer periphery of the plastic lens PL is held, and the gate portion (not shown) extending from the flange portion PLa is cut to thereby remove the plastic lens. PL is completed (step S9).
[0066]
[Third Embodiment]
The optical element manufacturing apparatus according to the third embodiment will be described below. The apparatus of the second embodiment is a modification of the apparatus of the first embodiment with respect to the movable shape.
[0067]
FIGS. 11A and 11B are cross-sectional views of the movable mold 214 of the manufacturing apparatus according to the third embodiment. FIG. 11A shows a state before the initial release, and FIG. 11B shows a state after the initial release. At the time of initial release, the flange portion PLa around the plastic lens PL is pushed outward by the protruding pin 16. As a result, the plastic lens PL is initially released from the optical surface 314a of the movable mold 314, but the flange portion PLa is shallowly fitted in the groove 314b having a stepped portion at the bottom. That is, the plastic lens PL can be supported by the side wall extending in the protruding direction of the groove 314b, and the fall can be prevented.
[0068]
12 is a cross-sectional view showing a modification of the movable type shown in FIG. FIG. 12A shows a state before the initial release, and FIG. 12B shows a state after the initial release. At the time of initial release, the flange portion PLa around the plastic lens PL is pushed outward by the protruding pin 16. As a result, the plastic lens PL is initially released from the optical surface 414a of the movable mold 414, but the main body portion of the plastic lens PL is shallowly fitted to the optical surface 414a, and the side wall of the optical surface 414a. By using the support, it is possible to prevent the plastic lens PL from falling.
[0069]
FIG. 13 is a cross-sectional view showing still another modification of the movable type shown in FIG. FIG. 13A shows a state before the initial release, and FIG. 13B shows a state after the initial release. At the time of initial release, the flange portion PLa around the plastic lens PL is pushed outward by the protruding pin 16. The plastic lens PL is initially released from the optical surface 514a of the movable mold 514, but the flange portion PLa is shallowly fitted in the groove 514b having a stepped portion on the upper portion, and the plastic lens PL is dropped. Can be prevented.
[0070]
As described above, the present invention has been described according to the embodiment, but the present invention is not limited to the above embodiment. For example, the optical surface 14a forming the plastic lens PL has a sawtooth shape in cross section as shown in FIG. 2 and the like, but is not limited to this and has various shapes that cause diffraction and interference. Can do.
[0071]
Further, the optical element according to the present invention is not limited to application to an optical pickup device. That is, the objective lens 77 is not limited to being able to image information recording / reproducing light in common when recording or reproducing information on recording surfaces of different optical information recording media such as DVD and CD. It can be applied to various optical systems. That is, the plastic lens according to the present invention is, for example, a coupling lens (including a collimating lens) that reduces deterioration of spherical aberration caused by a change in environmental temperature in a plastic objective lens, or an environmental temperature by a diffraction effect. Objective lenses that can alleviate the deterioration of spherical aberration caused by changes, lenses that reduce aberration deterioration caused by changes in laser wavelength, and objective lenses that realize a large numerical aperture by increasing diffraction power It can be applied to various things. Further, the plastic lens can be used in a scanning optical system of a laser beam printer, a semiconductor laser and fiber coupling optical system in an optical communication apparatus, and a semiconductor laser application optical system of a barcode reading optical system. In addition, for optical systems that use visible light, such as photographic lenses and viewfinders, various examples of providing a step that exhibits a diffraction effect on a curved surface have been proposed, but compared to diffractive optical elements for semiconductor lasers. The effective area of the optical surface is large, and the workability by the mold may be deteriorated. However, these can be improved by applying a plastic lens as in the present invention.
[0072]
【The invention's effect】
As is apparent from the above description, according to the method and apparatus for manufacturing an optical element according to the present invention, the optical surface of the molded product can be prevented from becoming defective due to re-contact with cooling shrinkage. The optical characteristics can be prevented from deteriorating. In addition, it is possible to reliably hold a sprue or the like extending from the molded product at a desired timing after mold release, and it is possible to easily and reliably prevent the molded product from dropping during mold release by the protruding member.
[0073]
The optical element according to the present invention is formed by the above-described optical element manufacturing method and has good optical characteristics.
[Brief description of the drawings]
FIG. 1 is a block diagram conceptually illustrating the structure of a manufacturing apparatus according to a first embodiment.
FIG. 2 is a longitudinal sectional view for explaining the shapes and structures of a fixed mold and a movable mold.
FIG. 3 is a front view for explaining the arrangement of protruding pins provided in the movable mold.
FIG. 4 is a front view for explaining a modified example of the protruding pin provided in the movable mold.
FIG. 5 is a flowchart for explaining the operation of the manufacturing apparatus of FIG. 1;
6A is a diagram showing a state immediately after filling with a molten plastic resin, and is a diagram showing a state where a molded product is initially released from a movable mold, and FIG. 6C is a diagram showing molding. It is a figure which shows the state which made the product additionally mold release with respect to a movable type | mold.
FIGS. 7A to 7D are diagrams for explaining the cause of molding defects on the diffractive lens surface PLb formed on the plastic lens PL. FIGS.
FIG. 8 is a schematic configuration diagram of an optical pickup device.
FIG. 9 is a block diagram conceptually illustrating the structure of a manufacturing apparatus according to a second embodiment.
FIG. 10 is a flowchart for explaining the operation of the apparatus of the second embodiment.
FIGS. 11A and 11B are movable sectional views of an apparatus according to a third embodiment. FIGS.
FIGS. 12A and 12B are sectional views of another movable type of the apparatus according to the third embodiment. FIGS.
FIGS. 13A and 13B are sectional views of still another movable type of the apparatus according to the third embodiment. FIGS.
[Explanation of symbols]
12 Fixed type
12a Optical surface
14 Movable type
14a Optical surface
16 Extrusion pin
24 Movable drive unit
26 pin drive
32 Controller
MP Molten plastic resin
PL plastic lens
DP diffraction pattern
PLa flange part
PLb diffractive lens surface

Claims (10)

Filling a resin into a cavity formed by a first mold member having an optical surface having a fine pattern provided on a curved surface and a second mold member facing the first mold member;
A step of opening the mold by separating the first mold member relative to the second mold member when the resin in the cavity is solidified to a predetermined level or more;
After the mold opening process, and before the molded product shrinks and deforms by a fine pattern, a protrusion member provided so as to avoid the optical surface is protruded on the first mold member side, so that the resin in the cavity Releasing the molded product obtained from the optical surface of the first mold member;
A step of temporarily holding the released molded product in the state of being close to the first mold member,
When the molded product is released from the optical surface of the first mold member, the mold release distance by the protrusion of the protrusion member is equal to or greater than the uneven depth of the fine pattern, and the entire product is separated from the first mold member. A method for manufacturing an optical element, characterized by being smaller than the length .   2. The optical element manufacturing method according to claim 1, wherein the molded product having an optical surface released from the mold is held in proximity to the first mold member in a state of being shallowly fitted to the first mold member. Method. The releasing distance by the protruding member when releasing the molded product from the optical surface of the first mold member is the maximum with respect to the protruding direction of the portion extending in the protruding direction on the molding surface of the first mold member. 3. The method of manufacturing an optical element according to claim 2 , wherein the optical element is smaller than the length. Wherein during the releasing step or after step, of the first mold member from claim 1, characterized by further comprising the step of performing further spaced so by incremental opening from said second mold member to claim 3 The manufacturing method of the optical element as described in any one. After the incremental opening step, by further be projecting the projecting member, additional release of a state of being separated from the first mold member by further separating the molded article from the optical surface of the first mold member The method of manufacturing an optical element according to claim 4 , further comprising a step of performing a mold.   Filling a cavity formed by a first mold member having an optical surface with a fine pattern on a curved surface and a second mold member facing the first mold member;
  A step of opening the mold by separating the first mold member relative to the second mold member when the resin in the cavity is solidified to a predetermined level or more;
  After the mold opening process, and before the molded product shrinks and deforms by a fine pattern, a protrusion member provided so as to avoid the optical surface is protruded on the first mold member side, so that the resin in the cavity Releasing the molded product obtained from the optical surface of the first mold member;
  Temporarily holding the released molded product in the state of being close to the first mold member;
An optical element manufacturing method comprising:
  When the molded product is released from the optical surface of the first mold member, the mold release distance due to the protrusion of the protruding member is equal to or greater than the uneven depth of the fine pattern, and the molded product released from the mold is initially A method of manufacturing an optical element, characterized in that the optical element is held in a state of being separated from the first mold member by the support of the protruding member fitted into the molded product by a protrusion from the first mold member. The mold opening distance in the mold opening step is larger than the mold releasing distance due to the protrusion of the protruding member when the molded product is released from the optical surface of the first mold member. The method for manufacturing an optical element according to claim 6 . The method for manufacturing an optical element according to claim 1, wherein the first mold member is a movable mold, and the second mold member is a fixed mold. A first mold member having an optical surface on which a fine pattern is provided on a curved surface;
A second mold member disposed opposite the first mold member;
Resin supply means for filling a resin formed in the cavity formed by the first and second mold members;
A protruding member that is provided on the first mold member side avoiding an optical surface, and that can project on the inner surface side of the first mold member;
An opening and closing mechanism for relatively opening and closing the first and second mold members;
An advancing and retracting mechanism for operating the protruding member;
When the resin in the cavity is solidified to a predetermined level or more, the opening / closing mechanism is operated to open the mold by separating the first mold member relative to the second mold member, and the mold After the opening and before the molded product contracts and deforms by the fine pattern, the advancement / retreat mechanism is operated to project the protruding member, thereby obtaining the molded product obtained from the resin in the cavity. A device for manufacturing an optical element, comprising: a control device that releases the molded product from the optical surface of the mold member and temporarily holds the released molded product in a state of being close to the first mold member;
When the molded product is released from the optical surface of the first mold member, the mold release distance by the protrusion of the protrusion member is equal to or greater than the uneven depth of the fine pattern, and the entire product is separated from the first mold member. An optical element manufacturing apparatus characterized by being smaller than the length .   A first mold member having an optical surface on which a fine pattern is provided on a curved surface;
  A second mold member disposed opposite the first mold member;
  A resin supply means for filling a resin formed in the cavity formed by the first and second mold members;
  A protruding member that is provided on the first mold member side avoiding an optical surface, and that can project on the inner surface side of the first mold member;
  An opening and closing mechanism for relatively opening and closing the first and second mold members;
  An advancing and retracting mechanism for operating the protruding member;
  When the resin in the cavity is solidified to a predetermined level or more, the opening / closing mechanism is operated to open the mold by separating the first mold member relative to the second mold member, and the mold After the opening and before the molded product contracts and deforms by the fine pattern, the advancement / retreat mechanism is operated to project the protruding member, thereby obtaining the molded product obtained from the resin in the cavity. A control device for releasing the mold from the optical surface of the mold member and temporarily holding the released molded product in a state of being close to the first mold member;
An optical element manufacturing apparatus comprising:
  When the molded product is released from the optical surface of the first mold member, the mold release distance due to the protrusion of the protruding member is equal to or greater than the uneven depth of the fine pattern, and the molded product released from the mold is initially The apparatus for manufacturing an optical element is characterized in that it is held close to the first mold member in a state separated from the first mold member by the support of the protruding member fitted into the molded product by the amount of the protrusion from

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