JPH0463362B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lens body in which a gradient index lens portion is formed in a transparent substrate made of synthetic resin, glass, or the like.

BACKGROUND ART Conventionally, a cylindrical gradient index lens as shown in FIG. 1 has been known. In the lens shown in FIG. 1, the refractive index changes approximately in the square approximation in the radial direction from the central axis of the transparent cylindrical body 1 made of synthetic resin or glass. Therefore, the light ray 2 that is perpendicularly incident on one surface of the transparent cylindrical body 1
is focused or diverged within this transparent cylindrical body 1,
The light is emitted to the outside from the other surface and is focused into a spot at the focal point 3, for example, if the refractive index decreases in the radial direction from the central axis.

In addition to the cylindrical gradient index lens shown in FIG. 1, a gradient index lens using a transparent flat plate is also known. In such a flat plate-shaped gradient index lens, for example, the refractive index changes approximately in square approximation from the central plane in the thickness direction of a flat transparent substrate made of synthetic resin or glass toward both surfaces. There is. Therefore, light rays that are incident parallel to both surfaces of the transparent substrate from one side edge existing between the both surfaces of the transparent substrate are converged or diverged in the thickness direction of the substrate within the transparent substrate. is emitted to the outside from the other side edge existing between the both surfaces, and for example, when the refractive index decreases approximately in square approximation from the center plane in the thickness direction toward both surfaces, an emission line concentrated in

The cylindrical or flat plate-shaped gradient index lens described above is widely applied to peripheral devices for optical communication, such as optical coupling systems between semiconductor lasers and optical fibers, and attenuators or attenuators in the middle of optical fibers. It is applied to parallel lens bodies for inserting branch circuits. In addition, the gradient index lens described above is a linear or matrix-shaped lens body constructed by arranging unit lens parts in one or two dimensions under imaging conditions that can form an erect, equal-magnification real image. It is applied to the optical systems of copying machines and facsimile machines.

However, in the case of a conventionally known gradient index lens, the refractive index distribution is two-dimensional. For example, in the case of the cylindrical gradient index lens shown in FIG. 1, the refractive index gradually changes in the radial direction from the central axis on a virtual plane perpendicular to the central axis. There is no change in the direction along the central axis. In addition, in the case of the flat plate-shaped gradient index lens described above, the refractive index gradually changes from the center plane in the thickness direction toward both surfaces in the virtual plane perpendicular to the surface. There is no change in the direction of travel of the axis, ie in an imaginary plane parallel to the surface. Furthermore, since the manufacturing process for these lenses is complicated, they are not suitable for mass production.

In order to correct such drawbacks, the present inventors have provided a gradient index lens portion formed in a transparent substrate by internally diffusing a substance that changes the refractive index into the transparent substrate. He devised a lens body and published it in Japanese Patent Application No. 128390 (1983).
A patent application was filed as (see Publication No. 53702). According to the lens body configured in this way, the lens body including the gradient index lens portion can be manufactured in large quantities through a simple manufacturing process.

In this case, a plurality of the gradient index lens parts are provided on a common transparent substrate, and each gradient index lens part passes through one point on a common surface of the common transparent substrate and is connected to the common surface. It has an approximately semicircular refractive index distribution area in all vertical cross sections, and this approximately semicircular refractive index distribution area extends in the radial direction about the one point on the common plane. It is preferable to have a refractive index distribution that gradually changes toward . According to the lens body configured in this way, the plurality of gradient index lens portions provided in the lens body can be configured to have relatively small focal lengths and be compact. The gradient index lens portions can be aligned with each other easily and accurately.

Next, reference examples 1 and 2 shown in FIGS. 2 to 5 will be described regarding specific aspects of the lens body constructed in this way.

First, reference example 1 shown in FIGS. 2 to 4 will be explained. This gradient index lens body is basically manufactured through the steps shown in FIG. 2.
Note that although FIGS. 2 to 4 illustrate the state in which a single gradient index lens portion is manufactured,
In practice, it is preferable that a plurality of gradient index lens parts be simultaneously manufactured on a common transparent substrate in a manner similar to the case shown in FIG.

In FIG. 2, a mask 12 having a circular window or hole 12a at its center is formed on a transparent substrate 11 made of a dielectric material such as synthetic resin or glass. The material of this mask 12 is determined depending on the diffusion substance containing the diffusion source diffused through the holes 12a, but when using sulfate as the diffusion substance, for example, titanium or titanium oxide (TiO ₂ ) may be used.

For example, when TiO ₂ is used as the mask material, a TiO ₂ film is first formed on the entire surface of the substrate 11 by sputtering, vapor deposition, etc., and then a photoresistor film is covered with this TiO ₂ film. Next, a portion of this photoresist film corresponding to the hole 12a is exposed to light, and the exposed portion of the photoresist film is removed. Then of this removed part
By removing the TiO ₂ film with a hot phosphoric acid solution and then removing the remaining photoresist film, a transparent substrate 11 having a mask 12 as shown in FIG. 2 is obtained.
Note that the hole 12a does not necessarily have to be circular, and may be elliptical in accordance with the shape of the required gradient index lens portion.

Next, the diffusion source 1 is inserted into the substrate 11 through the hole 12a.
0 is diffused to form a predetermined refractive index distribution described below within the substrate 11.

An example of the refractive index distribution in the lens body is shown in FIGS. 3A and 3B. Figure 3A shows
FIG. 4 shows the refractive index distribution in the axial direction (z-axis direction) of the gradient index lens portion 13 of the lens body shown in FIG. It gradually decreases and changes in an arc shape as a whole. Also,
FIG. 3B shows the refractive index distribution in the direction orthogonal to the axial direction (i.e., the refractive index distribution in the x-axis direction and the y-axis direction at an arbitrary point z ₀ in the z-axis direction), and shows the refractive index distribution in the x-axis direction and the y-axis direction at an arbitrary point z 0 in the z-axis direction, and Accordingly, the refractive index gradually decreases, for example, by square approximation, resulting in a mountain-shaped distribution as a whole.

The methods for diffusing the diffusion source 10 into the substrate 11 to obtain a predetermined refractive index distribution can be broadly classified into the following two methods.

One method is to diffuse and transfer a monomer that copolymerizes with this polymer to change its refractive index onto a transparent substrate 11 made of a synthetic resin made of a transparent polymer, and then perform the above-mentioned copolymerization process. This method is used in Specific Example 1, which will be described later. Another method is to provide a transparent substrate 11 made of a glass plate containing first ions constituting a glass-modifying oxide such that the first ions contribute to an increase in the refractive index of the glass plate to a greater extent than the first ions. A method in which a second ion that can constitute a large glass-modified oxide is exchanged and diffused, and the second ion is replaced with the first ion,
This method is used in Examples 3 and 4 below.

When a parallel light ray 14 is made incident on one surface of the lens body shown in FIG.
The light is focused at point 3, emitted to the outside from the other surface, and focused into a focal point 15 in the form of a spot.

The glass body obtained through the manufacturing process shown in FIG. 2 has a convex lens effect, as shown in FIG. 4. However, in FIG. 2, if a diffusion source that contributes to a decrease in the refractive index of the substrate 11 is used,
A lens body having a concave lens effect can be manufactured. The refractive index distribution of a lens body having such a concave lens effect is as shown in FIGS. 3A and 3B, except that the directions of increase and decrease are reversed.

Next, to explain specific example 2 shown in FIG. It is suitable for arranging the lens portions in a line or matrix in a common transparent substrate, and FIG. 5 shows a case in which they are arranged in a matrix.

In FIG. 5, each unit lens 21 has substantially the same configuration as the lens body shown in FIG.
1 and are arranged in a matrix in the XY direction. In this case, the diameter of the hole 12a of the mask 12 is 1/3 to 1/2 of the vertical or horizontal length of the unit lens 21.
It may be of a certain extent.

In the case of the above-mentioned lens body shown in FIG. 5, the relative positions of the large number of gradient index lens parts 13 can be selected arbitrarily and with high precision depending on the shape of the mask 12. Furthermore, as shown in FIG. 4, it is possible to prevent as much as possible the misalignment of the optical axes that occurs when a large number of lens bodies each having a single gradient index lens portion are bonded and fixed together to form a matrix. Moreover, the entire structure can be made smaller than in this case.

Next, a specific example of the manufacturing process shown in FIG. 2 will be explained.

Specific example 1 By heating allyl diglycol carbonate (commonly known as CR-39) to which 3% benzoyl peroxide was added at 80°C for 35 minutes to half-polymerize it, 50
A transparent substrate with dimensions of mm x 50 mm x 3 mm was obtained. the above
The refractive index of CR-39 was 1.504.

After attaching multiple 1.0 mm thick polyethylene masks with multiple circular holes with a diameter of 3.9 mm in the center to the surface of the transparent substrate, a refractive index of 1.5775 was applied.
The transparent substrate was immersed in vinyl benzoate (VB) monomer at 80° C., and the monomer was diffused into the transparent substrate through the mask hole for 60 minutes to cause copolymerization. Next, this transparent substrate is heat-treated at 80° C. for several hours and its surface is polished to produce a flat lens body having a gradient index lens portion having the characteristics shown in FIGS. 3A and 3B. I got it.

The beam diameter is 1 from the front surface of this flat lens body.
When a helium-neon laser beam of mm was incident as a parallel beam, the incident light could be focused into a 25 μm spot at the focal point (focal length of approximately 30 mm).

Specific example 2 Optical glass commonly known as BK7 (SiO ₂ 68.9
wt%, _{B2O3 10.1} wt%, NaO8.8 wt%,
_K2O (8.6% by weight, BaO2.8% by weight) and 50
A glass flat plate with dimensions of mm x 50 mm x 5 mm was prepared as a transparent substrate. The refractive index of this glass plate is
It was 1.515.

Thickness 0.1μm with multiple circular holes 1mm in diameter
After forming a mask on the surface of the transparent substrate by sputtering _TiO2 , 30 mol% _{of Ti2SO4} ,
A mixed salt of 40 mol% ZnSO ₄ and 30 mol% K ₂ SO ₄ was heated at 600°C.
The transparent substrate was immersed in a molten salt heated and melted, and ions in the molten salt were exchanged and diffused through the mask hole for 80 hours. Next, this transparent substrate is subjected to a slow cooling operation to return to room temperature, and then taken out into the air, and then its surface is polished to obtain a gradient index type having the characteristics shown in FIGS. 3A and 3B. A flat lens body including a lens portion was obtained.

The beam diameter is 1 from the front surface of this flat lens body.
When a parallel beam of helium-neon laser light with a diameter of 5 mm was incident, the incident light could be focused into a 50 μm spot at the focal point (focal length of approximately 50 mm).

In addition, in the above-mentioned specific examples 1 and 2, a mask similar to the above-mentioned mask may be formed on the side edge and back surface of the transparent substrate, if necessary, prior to the diffusion movement or exchange diffusion process.

The present invention further improves the lens bodies in Reference Examples 1 and 2 described above so that lens bodies with small focal lengths can be mass-produced through a simple manufacturing process, and a transparent substrate first and second gradient index lens portions formed therein, the first gradient index lens portion applying a material that changes the refractive index to the common transparent substrate; The second graded refractive index lens portion is formed by internal diffusion from a surface, and the second gradient index lens portion is formed by applying a substance that changes the first refractive index in the thickness direction of the transparent substrate to the common transparent substrate. each of the first and second gradient index lens portions passes through one point on each of the one and other surfaces of the common transparent substrate and is formed by internal diffusion from the one and the other surfaces of the common transparent substrate. It has an approximately semicircular refractive index distribution area in all cross sections perpendicular to the other surface, and this approximately semicircular refractive index distribution area approximately connects the one point on the one and the other surfaces. The present invention relates to a lens body characterized by having a refractive index distribution that gradually changes from the center in the radial direction.

Next, an embodiment of the present invention will be described with reference to FIGS. 6 and 7 while referring to FIG. 2.
In the case of FIG. 7 and FIG. 7, the diffusion source is diffused from both sides of the transparent substrate.

7 and 8, masks 22 and 23 formed on both sides of the transparent substrate 11 are substantially the same as the mask 12 shown in FIG. Holes 22a and 23a formed in are vertically opposed to each other. Therefore, when the same diffusion as in the case of FIG. 2 is performed from both sides of the substrate 11, a pair of upper and lower gradient index lens portions 24 and 25 facing each other is formed as shown in FIG. The lens portions of both have the characteristics shown in FIGS. 3A and 3B.

As described above, the combination lens portion is composed of the first gradient index lens portion 24 and the second gradient index lens portion 25 that faces the first lens portion 24 in the thickness direction of the transparent substrate. According to the flat plate lens body, light emitted from one point is focused by one lens portion 24 or 25, and then further focused by the other lens portion 25 or 24 to form a spot. Because it is focused on
If the above combination lens portion is used as a condenser lens, a lens with a very short focal length can be provided.

In addition, in the above-mentioned Example, either of the above-mentioned Example 1 and 2 can be employ|adopted as a concrete manufacturing method of a lens body. Furthermore, only one combined lens portion consisting of the first and second lens portions 24 and 25 facing each other may be formed on one transparent substrate 11, or two or more combined lens portions may be formed, for example. , a large number of them may be formed in a line shape or matrix shape (see FIG. 5). Moreover, the transparent substrate 11 does not necessarily have to be flat, and may be semi-cylindrical or the like.

Furthermore, in the embodiments described above, the mask 22
and 23 may then be removed if necessary. However, if these masks are made of an opaque material, the remaining masks may cause the surface of the transparent substrate to be exposed to the later gradient index lens portions 24, 25.
It is possible to prevent light from entering the transparent substrate from other surfaces.

As described above, the present invention provides first
and a second graded index lens portion, each of which is arranged on one side and the other side of a common transparent substrate. In all the cross-sectional views passing through each point and perpendicular to the one and the other surfaces, there is an approximately semicircular refractive index distribution area, and this approximately semicircular refractive index distribution area is and has a refractive index distribution that gradually changes in the radial direction about the one point on the other surface. Therefore, the above-mentioned combined lens portion has an imaging effect based on the light refraction effect which is a superposition of the light refraction effect of the two cylindrical gradient index lenses and the light refraction effect of the two normal curved lenses. , it is possible to provide a lens with a smaller focal length than in the case of a single gradient index lens portion, and it can be constructed in a smaller size considering the smaller focal length.

In addition, each of the first and second gradient index lens portions has all cross sections passing through one point on one and the other surface of the common transparent substrate and perpendicular to the one and other surfaces, respectively. In the figure, the refractive index distribution area has an approximately semicircular shape, and this uneven semicircular refractive index distribution area gradually changes in the radial direction about the one point on the one and the other surfaces. They are formed in the common transparent substrate by internally diffusing a substance that changes the refractive index into the common transparent substrate so as to have a refractive index distribution. Therefore, the first and second gradient index lens portions are aligned with each other with reference to the one and the other surfaces during the internal diffusion, and there is no need to align them individually thereafter. The mutual alignment of the second gradient index lens portions can be performed easily and accurately. Further, the distance between the first and second gradient index lens portions facing each other can be kept almost constant permanently by simply selecting an appropriate thickness of the common transparent substrate.
For this reason, it does not change over time and remains unchanged regardless of how it is handled. In particular, the diameter is several hundred microns.
When configuring an extremely large array of thousands or tens of thousands of very small lens parts, each of which has a size of approximately Although it is practically impossible to construct the above array by aligning the distances between all the gradient index lens parts to a constant value, according to the present invention, the thickness of the entire common transparent substrate can be approximately reduced. By simply selecting a constant distance, the distances between the first and second gradient index lens portions can be permanently set to a substantially constant value for all lens pairs. Furthermore, since there is no air layer between the first and second gradient index lens parts facing each other and the parts are completely filled with the transparent solid constituting the common transparent substrate, the optical performance is improved even when foreign objects are present. There is no risk of causing changes in

Further, by internally diffusing a substance that changes the refractive index into the transparent substrate, the first and second gradient index lens parts are formed in a common transparent substrate, and in this case, the first and second gradient index lens parts are formed in a common transparent substrate. The isotropic and natural diffusion can be utilized as it is from around one point on one and the other surface of the transparent substrate. Therefore, a lens body comprising a first and second graded index lens portion that can be easily and accurately aligned with each other and a compact combined lens portion with a short focal length can be manufactured through a simple manufacturing process. Therefore, it can be manufactured in large quantities.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a conventionally known cylindrical gradient index lens. Figures 2 to 5 show a reference example of the present invention based on the invention of Japanese Patent Application No. 128390/1982. Perspective view, No. 3A
3B is a diagram showing the refractive index distribution in the axial direction of the gradient index lens portion same as above, and FIG. Figure 4 is a perspective view of a part of the same lens body as described above, with hatching partially omitted, and Figure 5 is a perspective view of a case where a large number of gradient index lens parts are arranged in a matrix on a common transparent substrate. FIG. 7 is a perspective view of a lens body of Reference Example 2, with a portion of the lens body longitudinally cut and hatching partially omitted; 6 and 7 show one embodiment of the present invention, FIG. 6 is a perspective view of the lens body, and FIG. 7 is a perspective view of the lens body shown in FIG. 6, with hatching partially omitted. FIG. In addition, in the symbols used in the drawings, 11...transparent substrate, 22, 23...mask, 22a, 23a
. . . Holes, 24, 25 . . . Gradient index lens portion.

Claims (1)

[Claims] 1. Comprising first and second gradient index lens parts formed in a transparent substrate, the first gradient index lens part containing a substance that changes the refractive index. The second gradient index lens portion is formed by internal diffusion from one surface of the common transparent substrate, and the second gradient index lens portion is connected to the first gradient index lens portion in the thickness direction of the transparent substrate. Each of the first and second gradient index lens portions is formed by internally diffusing a substance that changes the refractive index into the common transparent substrate from the other surface so as to face each other. A refractive index distribution area having an approximately semicircular shape in all cross sections passing through one point on each of the one and other surfaces of the common transparent substrate and perpendicular to the one and other surfaces, respectively; A lens body characterized in that the circular refractive index distribution region has a refractive index distribution that gradually changes in the radial direction about the one point on the one and the other surfaces.