JP2006321168A - Die for molding optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a precise optical element by molding the optical element apart from the misalignment and slant of an optical axis. <P>SOLUTION: A figuration of the optical element is precisely made by forming a molding surface 1a and a molding surface 2a in an upper die 1 and a lower die 2 respectively. A taper part 1b is formed at the outside of the molding surface 1a of the upper die 1 by a predetermined angle θ concurrently with the molding surface 1a. Likewise, a reentering taper part 2b is formed at the outside of the molding surface 2a of the lower die 2 by a predetermined angle θ concurrently with the molding surface 2a. A pressure face part 1c which contacts with a pressing plate 7 of the upper die 1 is spherical where its apex is on the center line of the molding surface 1a of the upper die 1 so that a weight is applied at the one point when the optical element is molded. The thickness of the molded optical element is defined by fitting the taper part 1b to the taper part 2b. Since the misalignment and slant of the optical axis might arise when fitting the taper part 1b to along the taper part 2b while the lower die 2 is combined with the upper die 1, the misalignment and slant of the optical angle after molding is prevented according to the present invention because the taper part 1b is pressed in conformity with along the taper part 2b owing to the spherical figure of the pressure face part 1c of the upper die 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical element molding die for molding an optical element used in an optical apparatus.

  In recent years, optical elements used in optical devices have been molded using optical element molding dies and are mass-produced by various companies. With the increase in capacity, performance, and miniaturization of optical equipment, the precision of each part of the optical element has become strict, and the precision of each part of the optical element molding die and the precision when combined are also strict. It has become to.

  In order to obtain a highly accurate optical element molded product with little optical axis deviation and inclination as an optical element, it is important to suppress deviation and inclination of the axial centers of molding surfaces in the molding die. As means for achieving this, for example, as described in Patent Document 1, a method of regulating the deviation of the axis of the molding die and the inclination of the axis by a body mold is disclosed.

  FIG. 7 shows a cross-sectional view of a molding die for molding an optical element by a conventional method disclosed in Patent Document 1. As shown in FIG. 7, the body mold 3 is made of a predetermined ceramic material, and a through hole 3a is provided in the shaft center. The through-hole 3a serves as a cavity for molding the optical element material 4 into a desired optical element shape, and maintains the upper mold 1 and the lower mold 2 fitted to the body mold 3 from the opening portions at the predetermined positional relationship. To do. That is, it has a function of keeping the deviation and inclination of the shaft centers of the lower mold 2 and the upper mold 1 within desired accuracy.

Further, the insertion depth of the upper mold 1 is such that the flange portion 6 of the upper mold 1 abuts on the upper surface of the body mold holder 5. That is, the thickness of the optical element material 4 after molding is regulated and controlled by the flange portion 6 of the upper mold 1 and the body mold holder 5.
Japanese Patent Publication No. 6-49580

  However, the conventional optical element molding apparatus has the following problems. As shown in FIG. 7, the axial displacement and the inclination of the optical element to be molded are regulated by the portion where the upper mold 1 slides in the through hole 3 a of the body mold 3. Therefore, when the axial misalignment or inclination of the optical element to be molded is not within the desired accuracy, the body mold 3 and the upper mold 1 need to be adjusted or remade.

  In this case, the through-hole 3a of the body mold 3 and the upper mold 1 and the lower mold 2 are slid and combined, and a clearance for that is required. As a result, there is a problem that the completed product has a deviation or inclination of the axial center corresponding to the clearance.

  The present invention is directed to solving the problems of the prior art, and an object of the present invention is to provide a highly accurate optical element by molding an optical element from which axial misalignment and inclination are removed.

  In order to achieve the above object, an optical element molding die according to claim 1 according to the present invention is an optical element molding die for molding an optical element by pressing with an upper mold and a lower mold. A restriction shape portion is provided outside the lower mold optical element molding surface.

  Further, the optical element molding die described in claim 2 is the optical element molding die according to claim 1, wherein the upper and lower mold regulating shape portions are either a semicircular shape or a tapered sectional shape, Alternatively, the cross-sectional shape is a combination of a semicircular shape and a tapered shape.

  Further, in the optical element molding die according to claims 3 and 4, in the optical element molding die according to claims 1 and 2, the pressure surface portion of the upper mold that comes into contact with the pressurizing means that pressurizes the upper mold is made spherical. The spherical center is on the optical axis of the upper optical element molding surface, and the upper and lower mold restricting shapes have a tapered cross-sectional shape, and the tapered cross-section and the optical element are pressed. The angle between the surface perpendicular to the molding direction is 5 ° or more and 75 ° or less.

Further, in the optical element molding die according to any one of claims 5 to 7, in the optical element molding die according to claims 1 to 4, the restriction shape portions of the upper die and the lower die have groove portions for air venting, The upper mold and lower mold materials are cemented carbides mainly composed of tungsten carbide (WC), silicon carbide (SiC), titanium nitride (TiN), titanium carbide (TiC), chromium carbide (Cr ₃ C ₂ ), cermet mainly composed of alumina (Al ₂ O ₃ ), or alumina (Al ₂ O ₃ ), sapphire (Al ₂ O ₃ ), chromium carbide (Cr ₃ C ₂ ), silicon nitride (Si ₃₎ N _4), the use of any of ceramics mainly boron nitride (BN), further, the regulation shape of the regulating members of the upper and lower molds, the upper and lower molds Characterized by simultaneous machining an optical element molding surface in each.

  According to the above-described configuration, it is possible to control the shift and inclination of the axial center at the time of molding in the upper mold and the lower mold of the optical element by providing the restriction shape outside the molding surfaces of the upper mold and the lower mold. It becomes possible, and fine adjustment of the thickness of the optical element can be controlled by simultaneously processing the optical element molding surface and the restriction shape.

  According to the present invention, it is possible to eliminate misalignment or inclination of the upper and lower axes of the optical element during molding, and it is possible to finely adjust the thickness of the optical element. There is an effect that it is possible to provide a high-accuracy optical element that can cope with higher performance of the projector.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view showing a schematic configuration of an optical element molding die according to Embodiment 1 of the present invention. Here, components having the same functions corresponding to the components described in FIG. 7 showing the conventional example are given the same reference numerals, and the same applies to the following drawings.

  As shown in FIG. 1, the optical element molding die is composed of an upper die (first die) 1, a lower die (second die) 2, and a body die 3. The upper mold 1 and the lower mold 2 are made of a cemented carbide mainly composed of tungsten carbide (WC), for example, and are formed with a molding surface 1a and a molding surface 2a, respectively, and are ultra-precision processed into a desired optical element shape. Yes. Further, a convex taper portion 1b having a tapered cross section with a predetermined taper angle θ is simultaneously processed with the molding surface 1a as a regulating shape portion outside the molding surface 1a of the upper mold 1.

  Similarly, on the outside of the molding surface 2a of the lower mold 2, a concave taper portion 2b having a tapered cross section having the same taper angle θ as the taper portion 1b of the upper mold 1 is formed as a regulation shape portion. It is formed by simultaneous processing with 2a. Here, in the first embodiment, the taper angle θ of the surface of the taper portion 1b and the surface of the taper portion 2b is the same angle, but is not necessarily limited thereto.

  FIG. 2 shows the arrangement of the mold and the grindstone and the trajectory of the grindstone at the time of ultra-precision machining of the optical element shape. FIG. Represents. As shown in FIGS. 2A and 2B, the lower mold 2 and the processing tool grindstone 10 are tilted by a predetermined angle with respect to the rotating shaft 11 of the lower mold 2 that is the workpiece. The lower mold 2 is rotated about the rotating shaft 11, and the grindstone 10 is rotated at a high speed about the grindstone rotating shaft 12. Then, the grindstone 10 is moved relatively on the locus 10a with respect to the lower mold 2, and the molding surface 2a of the lower mold 2 and the tapered portion 2b of the lower mold 2 are simultaneously processed. At this time, in order to further improve the surface accuracy of the molding surface 2 a, two or more grindstones 10 may be attached, and the molding surface 2 a and the tapered portion 2 b may be processed by separate grindstones 10. However, it will be processed at the same time with one attachment.

  With the above configuration, by simultaneously processing the molding surface 2a for controlling the thickness of the optical element and the tapered portion 2b used for the axial alignment of the optical element, the thickness of the optical element is controlled, Tilt can be removed.

  As shown in FIG. 1, the pressure surface portion 1c of the upper mold 1 that contacts the pressure plate 7 that pressurizes the upper mold 1 by the pressing means 9 has a vertex on the center line of the upper mold 1, that is, the molding surface 1a of the optical element. A predetermined spherical shape passing through the center of the optical element (in the first embodiment, a spherical surface having a radius of “16 mm” with respect to a flat surface having a diameter of “16 mm”) is provided, and a weight is applied to one point when the optical element is molded. ing. Further, the body mold 3 serves as a guide for the upper mold 1 and the lower mold 2 during molding, and a through hole 3 a having a predetermined tolerance from the outer diameter of the upper mold 1 and the lower mold 2 is formed.

  Using the above optical element molding die, the thickness of the molded optical element is determined by the taper portion 1b of the upper mold 1 and the taper portion 2b of the lower mold 2 coming into contact with each other. Further, the deviation and inclination of the optical axis can be eliminated by combining the tapered portion 1b along the tapered portion 2b when the upper die 1 is combined with the lower die 2. Further, because the predetermined spherical shape provided on the pressure surface portion 1c of the upper die 1 is pressurized so that the tapered portion 1b of the upper die 1 is aligned with the tapered portion 2b of the lower die 2 at the time of molding. Further, the optical axis after the molding is configured to eliminate the deviation and inclination of the optical axis.

  Further, the lower limit value of the taper angle θ is an angle at which the functions of aligning the upper die 1 and the lower die 2 are minimized, and as a result of various experiments, the taper angle θ is 5 °. The upper limit value can be derived from the relationship between the strength of the mold material and the molding load. In the first embodiment, the mold material is cemented carbide and the molding load is about 100 kg, so the result shown in FIG. 3 is obtained. The taper angle θ is 75 °. Therefore, the taper angle θ may be in the range of 5 ° to 75 °. As a comparative example, if a mold having a taper angle θ of 80 ° is molded, the mold is destroyed, and if a mold having a taper angle θ of 3 ° is molded, a sufficient axis alignment function cannot be obtained. The optical element performance could not be satisfied.

  FIG. 4 and FIG. 5 are diagrams showing an example of a groove for removing air when molding an optical element. 4 and 5 show a predetermined air vent groove 2c in the tapered portion 2b of the restriction shape portion of the lower mold 2, (a) is a top view, and (b) is a side view. 4A and 4B, four grooves having a width of 0.6 mm are provided in a radial pattern, and air is discharged during molding. 5 (a) and 5 (b), four grooves 2c having a width of 0.6 mm are directed toward the outer periphery from the arc-shaped groove 2d having a width of 0.4 mm so that air can escape from all directions of the optical element. It is provided in a radial pattern to discharge air during molding.

  Needless to say, the shape of the air vent groove 2c is not necessarily limited to this. In the first embodiment, the air vent groove 2c is provided only in the lower mold 2, but it may be provided only in the upper mold or both. However, when it is not particularly necessary for molding the optical element, for example, when the filling rate of the optical element material 4 is low, the air vent groove 2c is not necessary.

  When the lens was molded using the optical element molding die of Embodiment 1 and the conventional optical element molding die shown in FIG. 7 as a comparative example, the lens was obtained in the molding die of Embodiment 1. The axial displacement between the first and second surfaces of the lens was as good as 1 μm or less, but the lens obtained by the conventional optical element molding die was caused by the clearance between the upper mold 1, the lower mold 2 and the body mold 3. Axial misalignment was 2 to 4 μm, and predetermined optical performance could not be obtained.

  FIG. 6 is a cross-sectional view showing a schematic configuration of an optical element molding die according to Embodiment 2 of the present invention. As shown in FIG. 6, the optical element molding die includes an upper mold 1, a lower mold 2, and a body mold 3. The upper mold 1 and the lower mold 2 are made of silicon carbide (SiC), and are formed with a molding surface 1a and a molding surface 2a, respectively, and are ultra-precision processed into a desired optical element shape. In addition, a concave semicircular part 1e having a semicircular cross section with a predetermined radius is processed simultaneously with the molding surface 1a as a regulating shape part on the outer side of the molding surface 1a of the upper mold 1. Similarly, a convex semicircular portion 2e having a semicircular cross-sectional shape with a predetermined radius is formed on the outer side of the molding surface 2a of the lower mold 2 simultaneously with the molding surface 2a. Has been.

  The body mold 3 serves as a guide for the upper mold 1 and the lower mold 2 during molding, and a through hole 3 a having a predetermined tolerance from the outer diameter of the upper mold 1 and the lower mold 2 is formed.

  The thickness of the optical element molded using the optical element molding die described above is determined by the semicircular part 1e of the upper mold 1 and the semicircular part 2e of the lower mold 2 coming into contact with each other. Further, the deviation and inclination of the optical axis can be eliminated by combining the semicircular portion 2e of the lower die 2 and the semicircular portion 1e of the upper die 1 when the upper die 1 is combined with the lower die 2. .

  Here, also in the second embodiment, when the lens is molded using the optical element molding die as in the first embodiment, the axial displacement between the first and second surfaces of the obtained lens is 1 μm. It was as good as below.

In addition, as an example of the mold material in the first and second embodiments, a cemented carbide mainly composed of tungsten carbide (WC), silicon carbide (SiC) is used, but an optical mirror surface is obtained, and an optical element material is obtained. For example, titanium nitride (TiN), titanium carbide (TiC), chromium carbide (Cr ₃ C ₂ ), alumina (Al ₂ O ₃ ) cermet, alumina (Al ₂ O ₃ ), sapphire (Al ₂ O ₃ ), chromium carbide (Cr ₃ C ₂ ), silicon nitride (Si ₃ N ₄ ), and die such as ceramics mainly composed of boron nitride (BN) Was able to achieve the same effect.

  In the first and second embodiments, the shape of the tapered portion or the semicircular portion having a predetermined angle is used as the shape that regulates the shift or inclination of the shaft center. You may comprise combining.

  The optical element molding die according to the present invention eliminates the deviation and inclination of the upper and lower mold axes of the optical element at the time of molding, can finely adjust the thickness of the optical element, and is used for optical equipment It is useful for molding.

Sectional drawing which shows schematic structure of the optical element shaping die in Embodiment 1 of this invention The arrangement of the mold and the grindstone and the trajectory of the grindstone at the time of ultra-precision machining of the optical element shape according to the first embodiment are shown, and (a) is a top view and (b) is a side view of an example when machining the lower mold. Figure The figure which shows the relationship between the shaping | molding weight of the shaping die in this Embodiment 1, and a cemented carbide material (A) which shows the example of arrangement | positioning of the groove | channel for air removal in this Embodiment 1, (b) is sectional drawing. (A) is a top view and (b) is a cross-sectional view showing another arrangement example of the air vent groove in the first embodiment. Sectional drawing which shows schematic structure of the optical element shaping die in Embodiment 2 of this invention Sectional drawing which shows the structure of the shaping die which shape | molds the conventional optical element

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Upper mold | type 1a, 2a Molding surface 1b, 2b Tapered part 1e, 2e Semicircle part 2 Lower mold | type 2c, 2d Groove 3 Body mold | type 3a Through-hole 4 Optical element material 5 Body mold holder 6 Flange part 7 Pressure plate 8 Heater 9 Addition Pressure means 10 Grinding wheel 10a Trajectory 11 Rotating shaft 12 Grinding wheel rotating shaft

Claims (7)

In an optical element molding die for molding an optical element by pressing with an upper mold and a lower mold,
An optical element molding die, wherein a restriction shape portion is provided outside the optical element molding surfaces of the upper mold and the lower mold.   The restriction shape portion of the upper die and the lower die has a cross-sectional shape that is either semicircular or tapered, or a cross-sectional shape that is a combination of semicircular and tapered shapes. Optical element molding die.   The pressure surface portion of the upper mold that is in contact with a pressurizing unit that pressurizes the upper mold is formed into a spherical shape, and the center of the spherical shape is on the optical axis of the optical element molding surface of the upper mold. 3. An optical element molding die according to 1 or 2.   The upper die and the lower die restricting shape part have a tapered cross-sectional shape, and an angle formed by the tapered cross-section and a surface perpendicular to the pressure molding direction of the optical element is 5 ° to 75 °. The optical element molding die according to claim 1 or 2, wherein the optical element molding die is provided.   The optical element molding die according to any one of claims 1 to 4, wherein the restriction shape portions of the upper die and the lower die have a groove portion for air venting. The material of the upper mold and the lower mold is cemented carbide mainly composed of tungsten carbide (WC), silicon carbide (SiC), titanium nitride (TiN), titanium carbide (TiC), chromium carbide ( Cermet containing Cr ₃ C ₂ ), alumina (Al ₂ O ₃ ) as a main component, or alumina (Al ₂ O ₃ ), sapphire (Al ₂ O ₃ ), chromium carbide (Cr ₃ C ₂ ), silicon nitride (Si _3. The optical element molding die according to claim 1, wherein any one of ₃ N ₄ ) and ceramics containing boron nitride (BN) as a main component is used.   The restriction shape of the restriction shape portion of the upper die and the lower die is processed simultaneously with the optical element molding surface in each of the upper die and the lower die. The optical element molding die described.

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