JP4132980B2 - Mold for optical element molding - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a molding die used when a high-precision optical element such as an aspheric lens is manufactured by press molding.
[0002]
[Prior art]
In recent years, in lenses used for optical communication and the like, accuracy required for surface accuracy, decentering, tilt, and the like of lenses has become increasingly strict in order to improve light coupling efficiency. In addition, these lenses are becoming aspherical at the same time as the lens diameter is reduced for high accuracy and miniaturization.
[0003]
In a lens that focuses light emitted from a laser diode onto an optical fiber, the lens is fixed to a stainless steel lens barrel, and this lens with a lens barrel is fixed to the laser diode module by welding with a YAG laser. . When manufacturing such a lens with a lens barrel, a press molding method capable of simultaneously molding an aspheric lens and fixing the aspheric lens to the lens barrel is widely adopted.
[0004]
FIG. 2 shows an example of a conventional mold used when molding a lens with a lens barrel.
[0005]
The fixed die 21 is mounted in a mounting hole provided at the center of the first support ring 23. The moving die 22 is mounted in a mounting hole provided at the center of the second support ring 24. Each mounting hole is formed with a portion whose inner diameter is enlarged at each inlet portion, and the lens barrel 12 is accommodated inside thereof.
[0006]
After mounting the lens barrel 12 on the outer periphery of the distal end portion of the moving die 22, a glass molding material is set on the moving die 22. Next, the moving die 22 is brought close to the fixed die 21, and the molding material is heated together with the fixed die 21, the moving die 22, the first support ring 23 and the second support ring 24 in that state. When the molding material is stabilized at a predetermined molding temperature, the moving die 22 is further advanced, a press load is applied between the moving die 22 and the fixed die 21, and the shape of the mold surface is transferred to the molding material to mold the lens 11. To do. At the same time, the molding material spreads in the lateral direction and is pressed against the inner surface of the lens barrel 12, and the lens 11 is fixed inside the lens barrel 12.
[0007]
(Problems of conventional technology)
The lens with the lens barrel used in the laser diode module has a very high required accuracy for the amount of deviation between the central axis of the lens barrel 12 and the central axis of the lens 11 in order to facilitate positioning with respect to the laser diode module. Tough. In the conventional mold, positioning of the lens barrel 12 with respect to the lens 11 is performed by a fitting portion between the inner diameter of the lens barrel 12 and the outer diameter of the movable die 22. However, since the length of this fitting part cannot be ensured sufficiently, high-precision positioning is difficult. In addition, when a thin barrel is used, there is a problem that the barrel swells due to the pressure of the molding material during press molding.
[0008]
[Problems to be solved by the invention]
The present invention has been made in view of the problems of conventional molds used in the press molding of a lens with a lens barrel as described above, and the object of the present invention is to improve the accuracy of lens mounting on the lens barrel. The object is to provide a high mold for molding optical elements.
[0009]
[Means for Solving the Problems]
The mold for molding an optical element of the present invention is
At the same time as molding a glass optical element using a pair of dies, an optical element molding die used when fixing a lens barrel to the outer periphery thereof,
A first support ring for supporting the first die from the outer peripheral side;
A second support ring for supporting the second die from the outer peripheral side;
A third support ring that is mounted around the tip portion of the second die, fits inside the second support ring, and supports the lens barrel from its rear end surface and outer peripheral surface;
It is provided with.
[0010]
According to the optical element molding die of the present invention, the third support ring is positioned on the outer peripheral surface of the tip portion of the second die, and the lens barrel is positioned on the inner peripheral surface of the third support ring. Therefore, sufficient dimensions can be secured for the length of the fitting portion of the third support ring with respect to the second die and the length of the fitting portion of the lens barrel with respect to the third support ring. The center axis of the cylinder can be exactly matched to the center axis of the second die. Further, since the lens barrel is supported by the third support ring from the outer peripheral surface thereof, if the rigidity of the third support ring is appropriately set, the lens barrel expands in the horizontal direction due to the pressure of the molding material during press molding. This can be prevented. Therefore, if a lens with a lens barrel is molded using the optical element molding die of the present invention, the central axis of the lens can be made to exactly coincide with the central axis of the lens barrel.
[0011]
Preferably, the third support ring is made of a material having a smaller coefficient of thermal expansion than the lens barrel. In this way, when the lens barrel is heated to the molding temperature together with the molding material, the clearance between the lens barrel and the third support ring changes in a direction that decreases, so the position accuracy of the lens barrel at the time of press molding Can be increased.
[0012]
Preferably, the third support ring has a clearance between the outer peripheral surface of the lens barrel and a predetermined value or less due to a difference in coefficient of thermal expansion at a temperature at which the optical element is molded. The inner diameter is determined so as to be in close contact with the outer peripheral surface of the lens barrel.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an example of an optical element molding die according to the present invention. In the figure, 1 is a fixed die (first die), 2 is a moving die (second die), 3 is a first support ring, 4 is a second support ring, 5 is a third support ring, and 11 is molded. A lens (optical element), 12 represents a lens barrel.
[0014]
The fixed die 1 is mounted in the first support ring 3. The moving die 2 is mounted in the second support ring 4. The third support ring 5 is fitted to the inlet portion of the second support ring 4 and is attached to the outside of the tip end portion of the moving die 2. The holes of the first and second support rings 3 and 4 to which the fixed die 1, the moving die 2 and the third support ring 5 are attached are processed at the same time, and each component is centered with high accuracy. Further, a counterbore hole having an inner diameter larger than the outer diameter of the distal end portion of the moving die 2 is provided on the distal end surface of the third support ring 5. A part of the tip of the moving die 2 protrudes upward from the bottom of the counterbore. The lens barrel 12 is attached to the inside of the counterbore and attached to the outside of the distal end portion of the movable die 2.
[0015]
In addition, the clearance of the fitting part of the fixed die 1 and the first support ring 3 and the fitting part of the moving die 2 and the second support ring 4 is about several microns. Further, the clearances of the fitting portion between the second support ring 4 and the third support ring 5 and the fitting portion between the third support ring 5 and the lens barrel 12 are also about several microns. The positioning of the second support ring 4 with respect to the first support ring 3 is performed by guide pins (not shown) provided on the peripheral portions of the both.
[0016]
The lens barrel 12 is inserted into a counterbore at the tip of the third support ring 5, and the end of the lens barrel 12 is attached to the outside of the tip of the movable die 2. A glass molding material is set on the moving die 2. Next, the moving die 2 is brought close to the fixed die 1, and the molding material is heated together with the fixed die 1, the moving die 2, the first support ring 3, the second support ring 4 and the third support ring 5 in an inert atmosphere. When the molding material is stabilized at a predetermined molding temperature, the movable die 2 is further advanced to apply a press load between the movable die 2 and the fixed die 1 to mold the lens 11. At the same time, the molding material spreads in the lateral direction and is pressed against the inner surface of the lens barrel 12, and the lens 11 is fixed inside the lens barrel 12.
[0017]
A lens with a lens barrel was manufactured using the molding die shown in FIG. For the lens barrel 12, a member made of stainless steel (SF20T) and having an outer diameter of 3.2 mm and an inner diameter of 2.4 mm was used. As the molding material, a ball material of L-BAL42 (manufactured by OHARA) was used. The third support ring 5 was made of carbide. The molding conditions were a molding temperature: 560 ° C. and a presser: 200 kgf. Since the molding temperature is 560 ° C., the clearance is set to 8 μm in consideration of the difference in thermal expansion coefficient between the lens barrel 12 and the third support ring 5 holding the lens barrel 12.
[0018]
When the center of the lens barrel 12 and the lens 11 was measured for 100 consecutive moldings, the conventional mold had a thickness of several tens of μm, which was several μm, and improved positioning accuracy was confirmed.
[0019]
【The invention's effect】
According to the optical element molding die of the present invention, a lens barrel can be attached to the outer periphery of the optical element with high positional accuracy at the same time as the glass optical element is molded.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of an optical element molding die according to the present invention.
FIG. 2 is a view showing an outline of a conventional optical element molding die.
[Explanation of symbols]
1 ... fixed die (first die),
2 ... Moving die (second die),
3 ... first support ring,
4 ... second support ring,
5 ... Third support ring,
11 ... Lens,
12 ... barrel,
21 ... fixed die,
22 ... Moving die,
23 ... first support ring,
24: Second support ring.

Claims (4)

At the same time as molding a glass optical element using a pair of dies, an optical element molding die used when fixing a lens barrel to the outer periphery thereof,
A first support ring for supporting the first die from the outer peripheral side;
A second support ring for supporting the second die from the outer peripheral side;
A third support ring that is mounted around the tip portion of the second die, fits inside the second support ring, and supports the lens barrel from its rear end surface and outer peripheral surface;
A mold for molding an optical element, comprising: 2. The optical element molding die according to claim 1, wherein the third support ring is made of a material having a smaller coefficient of thermal expansion than the lens barrel. The inner diameter of the third support ring is determined so that a clearance between the third support ring and the outer peripheral surface of the lens barrel is not more than a predetermined value due to a difference in coefficient of thermal expansion at a temperature at which the optical element is molded. The optical element molding die according to claim 2, wherein: The inner diameter of the third support ring is determined so that the third support ring is in close contact with the outer peripheral surface of the lens barrel due to a difference in coefficient of thermal expansion at a temperature when the optical element is molded. 2. An optical element molding die described in 1.

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