JPH047501A - Flat plate microlens - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a flat plate microlens such as a micro Fresnel lens, and particularly to a flat plate microlens as a replica lens by the 2P method.

(Prior Art) A replica lens system using the 2P method is known as one of the manufacturing methods for flat microlenses such as micro Fresnel lenses used as collimating lenses, lenses for coupling semiconductor lasers and optical fibers, etc. There is. 2P
The production of a flat plate microlens using the replica lens method is to place a photosensitive resin such as an uncured ultraviolet curing resin (UV resin) on a stamper (pressing die) having a blaze shape complementary to the blaze shape to be made. The photosensitive resin on the stamper is pressed against the stamper using a transparent substrate made of polycarbonate (PC), methacrylic resin, optical glass, etc. This pressing transfers the blaze shape of the stamper to the photosensitive resin, and the substrate This is done by curing the photosensitive resin by irradiating it with ultraviolet rays or the like from the side, and then peeling it together with the substrate from the stamper.

The flat microlens manufactured in this manner has a two-layer structure of a lens portion having a blaze shape and a substrate portion made of different materials.

(Problem to be Solved by the Invention) In a flat microlens, if the lens part and the substrate part have different refractive indexes, reflection will occur at the boundary between the lens part and the substrate part. The light transmission efficiency of the lens decreases.

For example, if the lens part is made of ultraviolet curing resin with a refractive index of 1.45 and the substrate part is made of polycarbonate with a refractive index of 1.584, reflection of about 4.4% will occur, and as a result, Light loss occurs.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a flat microlens with a two-layer structure that is improved so that no reflection occurs at the boundary between the lens portion and the substrate portion.

(Means for Solving the Problems) According to the present invention, the above-mentioned object is to provide a flat plate microlens having a two-layer structure of a lens part and a six-substrate part, in which the lens part and the substrate part are mutually connected to each other. This is achieved by flat plate microlenses characterized by being made of materials having the same refractive index.

(Function) According to the above configuration, since the refractive index of the lens portion and the substrate portion are equal to each other, reflection does not occur at the boundary between the two.

(Example) The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows a micro Fresnel lens as a flat plate microlens according to the present invention. The micro Fresnel lens is designated as a whole by the reference numeral 10, and has a two-layer structure including a lens portion 12 having a blaze shape and a transparent substrate portion 14.

The lens portion 12 is made of ultraviolet hardening resin, which is a photosensitive resin, and the substrate portion 14 is made of polycarbonate (PC).
, polyethylene (PS), polymethyl methacrylate (P
The refractive index of ultraviolet curing resin is generally 1.
．． 45 to 1.57°, whereas the standard refractive index of the above-mentioned transparent material constituting the substrate portion 14 is as shown in Table 1.

Table 1: Since the refractive index of the ultraviolet curing resin constituting the lens portion 12 and the above-mentioned synthetic resin constituting the substrate portion 14 changes depending on the blending method, the refractive index of the material constituting the lens portion 12 or the substrate portion 14 If one of the refractive indices constituting the two is selected, the other refractive index may be adjusted to be equal to the already selected refractive index by the blending method.

Ultraviolet curing resins do not contain norogens other than fluorine, sulfur,
It is known that the refractive index can be increased by adding an aromatic group, and it is known that the refractive index can be lowered by adding fluorine or silicon. Once the refractive index is determined, the refractive index of the ultraviolet curable resin may be adjusted by adding a refractive index adjusting component as described above so that it becomes equal to this refractive index.

Also, the substrate part 1 may be made of polycarbonate or methacrylic resin.
Similar to the ultraviolet curable resin, the refractive index of the transparent synthetic resin composing the lens part 4 is changed by adding the above-mentioned refractive index adjustment component, so the refractive index of the ultraviolet curable resin composing the lens part 12 is determined. Then, to match this refractive index,
□The refractive index of the synthetic resin constituting the substrate portion 14 may be adjusted.

For reference, Table 2 shows examples of methacrylate polymers having different refractive indexes.

Table 2 and FIG. 2 show an example of use of a two-layer micro Fresnel lens as a condensing lens for collimated light. When collimated light is focused by a micro Fresnel lens, the micro Fresnel lens 1 according to the present invention
At 0, since there is no difference in refractive index between the lens portion 12 and the substrate portion 14, no reflection occurs at the boundary between the two. This improves the light transmission efficiency of the lens, prevents interference, and makes it possible to focus collimated light up to the diffraction limit.

Further, FIG. 3 shows an example in which a micro Fresnel lens is used as a collimating lens for collimating light emitted from a semiconductor laser. Even in this case, in the micro Fresnel lens 10 according to the present invention, since there is no difference in refractive index between the lens portion 12 and the substrate portion 14, no reflection occurs at the boundary between the two, and the light from the lens Transmission efficiency is improved and loss of laser light is reduced. In addition, in Figure 3,
Reference numeral 16 indicates a semiconductor laser oscillator.

(Effects of the Invention) As can be understood from the above explanation, in the flat microlens according to the present invention, reflection occurs at the boundary between the lens part and the substrate part because the refractive index of the lens part and the substrate part are equal to each other. This improves the light transmission efficiency of the lens and reduces light loss.

[Brief explanation of the drawing]

FIG. 1 is an enlarged vertical cross-sectional view showing one embodiment in which the flat plate microlens according to the present invention is applied to a micro Fresnel lens, and FIGS. 2 and 3 are vertical cross-sectional views each showing an example of use of the micro Fresnel lens according to the present invention. It is a diagram. 10...Micro Fresnel lens 12...Lens section 14...Substrate section Patent applicant OMRON Corporation

Claims (1)

[Claims] 1. A flat plate microlens having a two-layer structure of a lens part and a substrate part, wherein the lens part and the substrate part are made of materials having the same refractive index. lens.