Method of manufacturing microlens array and microlens array
A method of manufacturing a microlens array comprising forming microlenses by dropping or injecting to a plurality of through holes formed on a substrate a liquefied lens material so as to dispose the lens material at each of the through holes, the lens material being curable and has a predetermined transmittivity and a predetermined viscosity.
This application is a divisional of U.S. patent application Ser. No. 10/126,726, filed Apr. 19, 2002.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates to a microlens array typically used in the fields of optical communication and optical packaging for coupling light emitted from a light source to an optical fiber or an optical waveguide, converting light emitted from the optical fiber or the optical waveguide into parallel rays or so focusing light beams to enter the optical fiber or the optical waveguide in an optical coupling system.
2. Related Art of the Invention
The microlens in general represents a fine lens having a lens diameter of not more than a several millimeters. Various methods relating to the microlens array including methods for manufacturing the same have been proposed in the art. The ion exchange diffusion method is widely known as a method for manufacturing the microlens array. In the ion exchange diffusion method, a dopant ion is selectively diffused on a multicomponent glass substrate.
The conventional ion exchange diffusion method will be described below with reference to
High temperature molten salt 104 shown in
The above-illustrated ion exchange diffusion method is suitable for forming a microlens having a diameter of from a several tens of microns to a several hundreds of microns; however, problems have been found with the method in manufacture of a microlens having a relatively large lens diameter or a lens effective diameter of from a several hundreds of microns to a several millimeters. More specifically, in order to prepare the relatively large microlens employing the ion exchange diffusion method, a depth of the diffusion must be a several hundreds of microns or more that is about the same as the size of the lens to be produced and it is necessary to conduct a heat treatment at a high temperature for a remarkably long time. Thus, in the ion exchange diffusion method, it is difficult to prepare lenses of a wide range of sizes having diameters from a several tens of microns to a several millimeters and, also, it is impossible to produce a microlens array having a focal length that is about the same as that of the diameter of the lens. Therefore, downsized and high-performance optical coupling elements have not been realized by the use of the ion exchange diffusion method.
SUMMARY OF THE INVENTIONIn view of the above problems, an object of the present invention is to provide a method of manufacturing a microlens array that realizes downsized and high-performance optical coupling elements to be used in the fields of optical communication and optical packaging.
One aspect of the present invention is a method of manufacturing a microlens array comprising forming microlenses by dropping or injecting to a plurality of through holes formed on a substrate a liquefied lens material so as to dispose the lens material at each of the through holes, the lens material being curable and has a predetermined transmittivity and a predetermined viscosity.
Another aspect of the present invention is the method of manufacturing a microlens array, wherein a curvature of each of the microlens is varied by adjusting whole or part of (1) configurations or sizes of the through holes of the substrate, (2) wettability between the substrate and the lens material, (3) a viscosity of the lens material and (4) a quantity of lens material in a droplet or in an injection shot.
Still another aspect of the present invention is the method of manufacturing a microlens array, wherein the lens material is dropped or injected substantially simultaneously by using nozzles that can drop or inject the lens material substantially simultaneously to the through holes.
Yet still another aspect of the present invention is the method of manufacturing a microlens array, wherein the lens material is a ultraviolet ray curable resin material, a thermosetting resin material, a thermoplastic material or a glass material.
Still yet another aspect of the present invention is the method of manufacturing a microlens array, wherein each of the through holes has a truncated conical shape or a step portion.
A further aspect of the present invention is the method of manufacturing a microlens array, wherein the microlenses are convex lenses.
A still further aspect of the present invention is the method of manufacturing a microlens array, wherein the microlenses are concave lenses.
A yet further aspect of the present invention is the method of manufacturing a microlens array, wherein all refractive indexes and/or a transmittivities of the lens materials to be dropped or injected to the plurality of through holes are not same.
A still yet further aspect of the present invention is the method of manufacturing a microlens array, wherein a whole or a part of the plurality of through holes vary in size, and the lens material is dropped or injected in accordance with the sizes of the through holes.
An additional aspect of the present invention is the method of manufacturing a microlens array, wherein the plurality of through holes are arranged on the substrate to give a closest packed structure, each of the through holes having the shape of a hexagon of a predetermined size.
A still additional aspect of the present invention is the method of manufacturing a microlens array, wherein the substrate is formed from silicone, a plastic material, a glass material, ceramic material, fiber material or a composite material.
A yet additional aspect of the present invention is a microlens multilayer formed by laminating a plurality of microlens arrays produced by the method of manufacturing a microlens array, wherein the plurality of microlens arrays are so laminated that optical axes of the microlenses of each microlens array coincide with the optical axes of the corresponding microlenses of another microlens array.
A still yet additional aspect of the present invention is a microlens array comprising a substrate in which a plurality of through holes are formed and a plurality of microlenses respectively disposed at the through holes in the substrate, wherein
-
- the microlenses are fixed to the through holes of the substrate by way of adhesion or deposition of a microlens material to a substrate material.
A supplementary aspect of the present invention is the microlens array, wherein the microlenses are formed of a ultraviolet ray curable resin material, a thermosetting resin material, a thermoplastic material or a glass material.
A still supplementary aspect of the present invention is the method of manufacturing a microlens array, wherein each of the through holes has a truncated conical shape or a step portion.
A yet supplementary aspect of the present invention is the method of manufacturing a microlens array, wherein the microlenses are convex lenses.
A still yet supplementary aspect of the present invention is the method of manufacturing a microlens array, wherein the microlenses are concave lenses.
Another aspect of the present invention is the method of manufacturing a microlens array, wherein all refractive indexes and/or a transmittivities of the lens material to be dropped or injected to the plurality of through holes are not same.
Still another aspect of the present invention is the method of manufacturing a microlens array, wherein a whole or a part of the plurality of through holes vary in size and a whole or a part of the microlenses vary in size in accordance with the sizes of the through holes.
Yet still another aspect of the present invention is the method of manufacturing a microlens array, wherein the plurality of through holes are arranged in the substrate to give a closest packed structure, each of the through holes having the shape of a hexagon of a predetermined size.
Still yet another aspect of the present invention is the method of manufacturing a microlens array, wherein the substrate is formed of any one of silicone, a thermoplastic material, a glass material, a ceramic material, a fiber material and a composite material.
A further aspect of the present invention is the method of manufacturing a microlens array, wherein each of the microlenses has a multilayer structure that consists of a plurality of layers varying in material and refractive index.
A still further aspect of the present invention is the method of manufacturing a microlens array, wherein each of the plurality of through holes in the substrate has a rectangular shape of a predetermined size and each of the microlenses that is formed by dropping has an anamorphotic or cylindrical configuration.
A yet further aspect of the present invention is the method of manufacturing a microlens array, comprising subjecting a surface of the substrate to an inactivating treatment so that a portion of the surface excluding the through holes has repelling properties to the lens material and the through holes have adhesive properties to the lens material.
A still yet further aspect of the present invention is the method of manufacturing a microlens array, wherein the surface of the substrate is caused to be uneven by the inactivating treatment.
BRIEF DESCRIPTION OF THE DRAWINGS
-
- 11, 31, 51, 61, 71, 81, 83, 85, 87, 91: substrates
- 32, 52, 62, 72: through holes
- 12, 35, 55, 56, 65, 73, 82, 84, 86, 88, 92, 93, 94, 95, 96, 97: lenses
- 33, 44: nozzles
- 101: multicomponent glass substrate
- 102: ion exchange control membrane
- 103: circular aperture
- 104: molten salt
- 105: ion exchange area
- 106: convex lens
Preferred embodiments of the present invention will be described below with reference to FIGS. 1 to 14.
(First Embodiment)
The convex lenses 12 have light transmitting properties and they are formed from a curable liquefied resin material or a thermoplastic material or a glass material that can be cured on the substrate 11.
The microlens array according to the first embodiment is characterized in that a lens material, which is the resin material or the heated and liquefied plastic material or glass material described above, is dropped or injected to the through holes formed on the substrate 11 and that the convex lenses are disposed by taking advantages of a surface tension of the lens material. Further, positions of the convex lenses can be set arbitrarily depending on positions of the through holes disposed on the substrate 11.
Particularly, the positioning of the convex lenses 12 on the substrate 11 is facilitated by dropping or injecting the lens material to the through holes after forming the through holes on the substrate 11. The positions and sizes of the though holes can be defined arbitrarily by employing a fine processing technique according to the substrate material and, therefore, it is possible to form the through holes with a remarkably high degree of precision. Further, it is possible to control optical characteristics of the lenses by properly selecting the refractive index of the lens material. Moreover, it is possible to control a curvature of each of the lenses by adjusting a viscosity of the lens material before curing and an amount of drop or injection of the lens material to each of the through holes.
Thus, the microlens array according to the first embodiment of the present invention is characterized in that the positions and the optical characteristics of the lenses are controlled simultaneously and with a remarkably high degree of precision. Further, it is possible to form lenses of a wide range of effective diameters of from about a several tens of microns to about a several millimeters by adjusting a wettability, a viscosity and an amount of drop of the lens material to the substrate material.
The microlens array according to the first embodiment of the present invention is remarkably advantageous in terms of the optical coupling since the focal length is about the same as that of the diameter of each of the lenses and both surfaces of the lens are open to air without contacting the substrate material.
Thus, the material used for forming the substrate 11 of the microlens array according to the first embodiment of the present invention is not necessarily an optical material having light transmitting properties such as the plastic material or the glass material. More specifically, it is possible to form the microlens array if the substrate 11 is not formed from the optical material. In the case where the substrate 11 is formed from a material other than the optical material, the substrate 11 functions as an optical mask for the lenses to be formed on the substrate, thereby preventing stray lights from entering the lenses, which is remarkably effective in practical use.
(Second Embodiment)
As shown in
Then, as shown in
The adhesive resin material 34, which is the lens material, is dropped sequentially to the through holes disposed on the substrate as shown in
(Third Embodiment)
A method of manufacturing microlens array according to a third embodiment of the present invention that is illustrated in
(Fourth Embodiment)
A method of manufacturing microlens array according to a fourth embodiment of the present invention that is illustrated in
As shown in
As shown in
γS=γSL+γL cos θ Equation 1
In Equation 1, γS is a surface tension of the solid, γSL is a surface tension of the liquid, γL is an interfacial tension, and θ is a contact angle.
When Lb is larger than Vb, the convex lenses as shown in
γS=γL cos θB, γS=γL sin θB [Equation 2]
When Lb is larger than Vb and each of the through holes has the truncated conical shape as shown in
γS=γL cos θC+γSL cos α, γL sin θC=γSL sin α. [Equation 3]
When Lb is equal to or smaller than Vb, the concaved lenses are formed as shown in
γS=γL cos θD, γSL=γL sin θD [Equation 4]
Thus, it is possible to form both of the convex lenses and the concaved lenses by properly adjusting the viscosity, the wettability to the substrate material and the dropping amount of the lens material. Further it is possible to produce lenses each having a large numerical aperture (NA) since the curvature of lenses can be changed as described above.
A basic conception of adhesiveness according to the present invention will be described below. When water or alcohol is dropped on a surface of a solid that has a relatively large surface energy such as a clean glass or metal, the liquid wets completely the surface of the solid. When a solid-gas interfacial energy is γSG, a gas-liquid interfacial energy is γLG and a solid liquid interfacial energy is γSL, the following Equation holds and the surface of the solid is not wet to repel the liquid.
γSG<γLG+γSL [Equation 5]
When a liquid spreads over a surface of a solid, the phenomenon is called “spread wetting”. To contrast, in the case where a liquid immerses into capillaries of a fiber or a paper, the phenomenon is called “immersional wetting”. In turn, in the case of the present invention, a liquid adheres on a surface of a solid in the form of spheres, and the phenomenon is called “adhesive wetting”.
The spread wetting occurs when water is dropped on a clean glass surface; however, it is possible to cause the adhesive wetting on the glass surface by subjecting the surface to a hydrophobication by using a cationic-activating agent. A change in a free energy ΔG with respect to each of the wettings is obtained by subtracting an interfacial energy that is lost by each of the wettings from an interfacial energy caused by each of the wettings. Particularly, the change in a free energy ΔG with respect to the adhesive wetting is represented by the following Equation.
ΔG=γSL−γSGγLG [Equation 6]
Here, since Equation 1 can be rewritten into γSG=γSL+γLG cos θ by using γSG and γLG, Equation 6 can be modified as follows.
ΔG=−γLG(1+cos θ) [Equation 7]
It is apparent from Equation 7 that the change in free energy with respect to the adhesive wetting can be represented as a coefficient for the surface tension of the liquid and a contact angle θ and it is possible to cause the adhesive wetting when ΔG is a positive integer. Accordingly, the adhesive wetting can occur irrespective of θ. However, a reduction in the free energy is relatively large and the wetting tends to occur if a value of θ is relatively small.
(Fifth Embodiment)
In order to control the lens curvature, it is possible to use through holes 62 each having a step-like profile in place of the tapered through holes. Examples of forming convex lenses 65 are described hereinbefore; however, it is possible to form not only the convex lenses but also concaved lenses and non-spherical lenses by adjusting the amount drop or injection of the lens material.
In the above embodiments, cases of using the adhesive resin material as the lens material for the microlenses composing the microlens array are described; however, it is also possible to use a plastic material, a glass material or the like as the lens material by changing the substrate material, the cure time and the dropping amount.
Cases of using the plastic material, glass material and so forth will be described below with reference to
Also, it is possible to use a silicone substrate, a ceramic material, a plastic material, a fiber reinforced plastic, a fiber material such as a carbon fiber or a composite material composed of the above materials as the substrate material in place of the glass material. Examples of the fiber composite material include a glass fiber reinforced plastic (GFRP) that has widely been used. A composite material obtainable by combining high-performance and high-functional materials is called “advanced composite material” (ACM), and it is possible to use as the substrate material an ACM comprising a reinforcing material such as a high-performance carbon fiber, an aramid fiber and like inorganic fibers and a whisker as well as a matrix such as various high-performance resins, metals and ceramics.
(Sixth Embodiment 6)
It is possible to produce a microlens array employing the production method described with reference to
A case of laminating two microlens arrays will be described below with reference to
(Eighth Embodiment)
Further, as shown in
As shown in
(Ninth Embodiment)
A manufacturing method of microlens array according to a ninth embodiment of the present invention will be described with reference to
(Tenth Embodiment)
A manufacturing method of microlens array according to a tenth embodiment of the present invention will be described with reference to
(Eleventh Embodiment)
A manufacturing method of microlens array according to an eleventh embodiment of the present invention will be described with reference to
The substrate to be used for the above embodiments is not limited to the glass substrate, and a monocrystal silicone substrate, a ceramic substrate, a plastic substrate, a fiber substrate, a metal substrate or a composite substrate can be used depending on the lens material to be used. It is apparent that the microlens array is obtainable by using any one of the above substrates provided that the method for forming the through holes and the lens material are properly selected.
As described above, it is possible to arbitrarily change the size of the microlens of the present invention depending on the size of each of through holes to be formed on the substrate, and it is possible to produce the microlenses of a wide range of sizes each of which has a diameter from a several tens of microns to a several millimeters. It is possible to control optical properties of the microlens array by way of the lens material to be dropped or injected to the substrate, and each of the microlenses thus obtained is remarkably advantageous in terms of the optical coupling since both surfaces of each of the lenses are open to air without contacting the substrate material. Accordingly, the usage of the microlens array of the present invention is not limited to the optical communication elements, and it is possible to apply the microlens array to the optical packaging substrates and also, widely to image information processing devices and liquid crystal display devices, for the optical coupling, optical signal processing, light beam conversion and the like.
As is apparent from the above description, the present invention provides the microlens array that realizes downsized and high-performance optical coupling elements to be used in the fields of the optical communication, the optical packaging and the like and the method of manufacturing the same.
That is, according to the present invention, it is possible to produce a microlens array of a wide range of lens diameters remarkably easily. Also, according to the present invention, the lenses are disposed at arbitrary positions with both surfaces of each of the lenses being open to air without contacting the substrate material and they are remarkably high in precision. Thus, the present invention realizes the downsized and high-performance optical coupling elements.
Claims
1. A microlens multilayer formed by laminating a plurality of microlens arrays produced by a method of manufacturing a microlens array according to the following steps:
- (a) dropping or injecting a liquefied lens material into a plurality of through holes formed on a substrate so as to dispose the lens material at each of the through holes, the lens material having a predetermined transmittivity and a predetermined viscosity, and
- (b) laminating the plurality of microlens arrays so that optical axes of the microlenses of each microlens array coincide with the optical axes of corresponding microlenses of another microlens array.
2. A microlens array comprising a substrate in which a plurality of through holes are formed and a plurality of microlenses respectively disposed at the through holes in the substrate, wherein
- the microlenses are fixed to the through holes of the substrate by way of adhesion or deposition of a microlens material to a substrate material.
3. The microlens array according to claim 2, wherein the microlenses are formed of a ultraviolet ray curable resin material, a thermosetting resin material, a thermoplastic material or a glass material.
4. The method of manufacturing a microlens array according to claim 2, wherein each of the through holes has a truncated conical shape or a step portion.
5. The method of manufacturing a microlens array according to claim 2, wherein the microlenses are convex lenses.
6. The method of manufacturing a microlens array according to claim 2, wherein the microlenses are concave lenses.
7. The method of manufacturing a microlens array according to claim 2, wherein all refractive indexes and/or a transmittivities of the lens materials to be dropped or injected to the plurality of through holes are not same.
8. The method of manufacturing a microlens array according to claim 2, wherein a whole or a part of the plurality of through holes vary in size and a whole or a part of the microlenses vary in size in accordance with the sizes of the through holes.
9. The method of manufacturing a microlens array according to claim 2, wherein the plurality of through holes are arranged in the substrate to give a closest packed structure, each of the through holes having the shape of a hexagon of a predetermined size.
10. The method of manufacturing a microlens array according to claim 2, wherein the substrate is formed of any one of silicone, a thermoplastic material, a glass material, a ceramic material, a fiber material and a composite material.
Type: Application
Filed: Sep 29, 2004
Publication Date: Feb 17, 2005
Inventor: Nobuki Itoh (Kitakatsuragi-gun)
Application Number: 10/952,954