JPS63303826A - Production of cluster type distributed index optical element - Google Patents

Abstract

PURPOSE:To obtain the title compact optical element having a short conjugate length by bundling plural glass rod stocks, heating and drawing the aggregate to fuse the glass rod stocks to each other. CONSTITUTION:The glass rod stock is dipped in the molten salt of KNO3, LiCl, Tl2SO4, etc., to exchange the ions of Na<+>, K<+>, etc., in the glass rod stock for the ions of Tl<+>, Li<+>, etc., and a glass rod stock 4a having a refractive index distribution is obtained. The aggregate 5a obtained by bundling plural glass rod stocks 4a is then drawn by a tension roller 7 while being heated by a heating furnace 6 to fuse the stocks to each other, and a cluster optical element 5b having a refractive index distribution and consisting of thin glass stocks 4b having a refractive index distribution is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing a collective type gradient index optical element in which a plurality of glass rods having a refractive index distribution are bundled and fixed.

(Prior Art) In recent years, with the development of micro-optics, collective gradient index optical elements have attracted attention and have come to be widely used in lens arrays for copying machines and facsimile machines.

A typical method for forming a refractive index distribution in a glass rod, which is a component of a collective type gradient index optical element, is a method of forming the refractive index by ion exchange in glass (Japanese Patent Publication No. 47-816).

This method will be explained below.

In this ion exchange treatment, TI" is usually used.

Ions having the effect of increasing the refractive index such as C8" and Li" are exchanged with ions having the effect of decreasing the refractive index such as Na' and Ni+. For example, when producing an optical element that has a refractive index distribution in the radial direction from the center of the cross section by ion exchange treatment of a glass rod with a circular cross section, in order to give it a light condensing effect (convex lens effect), is, T
Glass rod material containing “I”, Cs”, Li” etc.
, K'', etc., to remove Tl in the glass rod.
By exchanging Na''', r, etc. in the molten salt with Cs, Li+, etc., the refractive index decreases from the central axis of the glass rod toward the periphery. In order to have a diverging effect (concave lens effect), Na", K"
Glass rods containing Tl', Cs'', Li
Na” in the glass rod material by immersing it in molten salt containing “Na”, etc.
4 etc., and TI”, Cs”, Li” in the molten salt.
etc., so that the refractive index increases from the central axis of the glass rod toward the periphery.

The molten salt used in such ion exchange treatment is
N5NO3, KNOs, LICI, T12 S0
4.

[:5N03 etc.

Hereinafter, a conventional method for manufacturing a lens array will be described as an example of a collective type gradient index optical element using a glass rod having a refractive index distribution formed by the method described above.

First, in order to prevent flare, the outer peripheral side surface of a glass rod material having a refractive index distribution is made rough by etching or the like, and a light absorber is applied to the entire side surface. As this absorber, black paint or the like is usually used.

Next, as shown in FIG. 1, a lens array is manufactured by sandwiching and adhesively fixing this glass rod material 1 between a spacer 2 and a plate material 3. This lens array is used as an erecting equal-magnification lens in optical systems such as copying machines and facsimile machines.

(Problem to be Solved by the Invention) In the conventional technology as described above, for example, a large number of thin glass rods with a diameter of about 1 cm are aligned in the optical axis direction and arranged and adhesively fixed in large numbers with high precision without gaps. is very time consuming and
There is a problem of poor yield.

Furthermore, since such a small diameter glass rod is easily broken, it requires careful handling in each manufacturing process, resulting in high costs.

Another problem with conventional techniques is that it is difficult to form a distribution with a large difference in refractive index in the radial direction of a glass rod having a small diameter. For example, in the method described above in which ions in the glass rod are exchanged with ions in the molten salt to form a refractive index distribution in the glass rod, the diameter of the glass rod is small. In this case, the ions in the molten salt reach the central axis of the glass rod in a short time, so only a distribution with a small difference in refractive index near the central axis and near the surface can be formed.

The present invention was made in view of the above-mentioned interlayer points, and its purpose is to provide a compact glass rod with a short conjugate length, which is made of a glass rod material with a small diameter and a large distribution of refractive index differences in the radial direction. An object of the present invention is to provide an easy method for manufacturing a collective gradient index optical element.

(Means for Solving the Problems) The above-mentioned object of the present invention is to provide a method for manufacturing a collective type gradient index optical element in which glass rods having a refractive index distribution are bundled and fixed. This is achieved by a method for manufacturing a collective gradient index optical element, which includes the steps of heating and stretching a plurality of glass rods in a bundle and fusing the glass rods together.

The glass rod material processed in the present invention is difficult to break, is easy to handle, has a desired refractive index distribution, and is necessary for obtaining a rod-shaped optical element with a desired diameter by heating and stretching as described below. A thickness of about 100% is used. For example, one having a diameter of 1 mm to 5 ms is preferable.

When glass rods as described above are bundled and heated and stretched, the difference in refractive index near the central axis and near the surface does not change, but the glass rods can be fused together as a bundle with a reduced diameter. Such a bundle, for example, has a short conjugate length and is a collective gradient index optical element suitable for a compact lens array.

In the manufacturing method as described above, if a large number of glass rods are bundled and heated and stretched, the manufactured aggregate type gradient index optical element has the strength unique to an aggregate of glass rods, is difficult to break, and is The aggregate itself can be made thick enough to easily align the optical axis direction and arrange a large number of them with high precision without gaps, so the aggregate can be further bundled and bonded, heat-pressed, or heat-stretched. Accordingly, it is also possible to manufacture a large-area collective type gradient index optical element.

Hereinafter, the method of the present invention will be explained in more detail with reference to the drawings.

FIG. 2 is a schematic diagram showing an example of the method of the present invention. Nineteen thick glass rods 4a having a refractive index distribution are bundled into a regular hexagonal shape, and the aggregate 5a is heated in a heating furnace 6 and stretched by a tension roller 7 to produce a thin glass rod having a refractive index distribution. 4b, a regular hexagonal aggregated refractive index gradient optical element 5b is manufactured. In this method, the difference in refractive index between the thick glass rod 4a and the heated and drawn thin glass rod 4b near the central axis and near the surface hardly changes.

FIG. 3 is a sectional view of a regular hexagonal aggregated refractive index distribution optical element 5b made of thin glass rods 4b having a refractive index distribution manufactured as described above. This can be cut to any length and polished on both end faces to be used as a lens array, multi-fiber lens, etc.

Next, a method of providing a light absorber around a glass rod material will be described as an example of a case where prevention of flare is required in the collective type gradient index optical element manufactured according to the present invention.

FIGS. 4 and 5 are cross-sectional views showing a collective gradient index optical element that prevents flare.

The aggregated refractive index gradient optical element 9 is made by heating and stretching 19 glass rods 4a whose sides are covered with a glass light absorber 8 into a regular hexagonal shape, and is a sufficiently thin glass rod. 4b and an absorber 8 covering it.

The collective type gradient index optical element 11 includes one glass rod 4a.
While bundling 9 pieces into a regular hexagonal shape, IS is installed in all the gaps.
It is made by placing one film of A absorbent material and heating and stretching it, and consists of a sufficiently thin glass rod 4b and one film of ISA absorbent material.

Next, a method of using a second light absorber made of glass will be explained as one means for further improving the durability, heat resistance, and polishing workability of the aggregated graded index optical element manufactured according to the present invention. do.

FIG. 6 is a sectional view showing an example of using a second light absorber made of glass. The side surface of the thick glass rod material 4a having a refractive index distribution is covered with a glass light absorber 8, which is further covered with a second glass light absorber 12a having a low softening point, which consists of 19 straight glass rods. Aggregate 13a bundled into a hexagonal shape
is formed.

FIG. 7 is a sectional view showing an aggregate type gradient index optical element manufactured by heating and stretching such an aggregate. This aggregated refractive index distribution optical element 13b consists of a glass bar 4b covered with a light absorber 8 that has been made thinner by heating and stretching, and a second glass light absorber layer 12b that has flowed by heating and stretching and filled the gap. It consists of Such a collective gradient index optical element is excellent in durability, heat resistance, and polishing workability.

Furthermore, each of the collective type gradient index optical elements 5b19, 11, and 13b described above has a thickness that is difficult to break and easy to handle. It is also possible to manufacture a large-area aggregated refractive index gradient optical element by fixing it by heating and stretching.

FIG. 8 is a cross-sectional view showing an example of a large-area collective type gradient index optical element 14 manufactured as described above.

In addition, if a second light absorber with a low softening point is provided around the collective gradient index optical elements 5b and 9.11.13b before the above-mentioned process, the gaps will be filled and excellent durability will be achieved. , a large-area gradient index optical element having heat resistance and polishing workability can be manufactured.

The present invention has been described above using a method for manufacturing a regular hexagonal aggregated refractive index gradient optical element.Next, specific examples of methods for manufacturing other shapes will be described.

First, a specific example of a method for manufacturing a sheet-like collective graded refractive index optical element that is flexible enough to recover from bending within a certain bending radius will be described.

FIG. 9 is a schematic diagram showing a method for manufacturing a flexible sheet-like aggregated refractive index gradient optical element from an aggregate of glass rods arranged in a wedge shape.

Glass rods 4a covered with light absorbers 8 made of wood are arranged in a wedge shape to form an aggregate 15a, which is heated in a heating furnace 6 and stretched by a winding drum 16 to form a wedge-shaped aggregate. It is wound onto a winding drum 16 while forming a molded refractive index gradient optical element 15b. Note that the radius of the winding drum 16 is such that the wound wedge-shaped aggregated refractive index gradient optical element 15b is
It is preferable that the radius is within a range that allows recovery of the linearity.

FIG. 1θ is a cross-sectional view of a wedge-shaped aggregated refractive index gradient optical element manufactured as described above. This collective type gradient index optical element 15b consists of a glass rod 4b covered with an absorber 8 which has been made sufficiently thin by heating and stretching the glass rod.

FIG. 11 is a sectional view of the winding drum in the manufacturing method as described above. Wedge-shaped aggregated refractive index gradient optical elements 15t) are aligned and tightly wound on the surface of the winding drum 16 to form a sheet-like aggregate 15c. Since the convex portions and concave portions of each aggregate are combined in this aggregate, no deviation occurs in the thickness direction of the aggregate 15c. By fixing this aggregate 15c with an adhesive, removing it from the winding drum 16, cutting it to a predetermined size, and polishing it, a flexible sheet-like aggregate type gradient index optical element can be manufactured.

Furthermore, it is also possible to manufacture a large-area aggregated refractive index gradient optical element by laminating a plurality of such sheet-like aggregated refractive index gradient optical elements and fixing them by adhesive fixation, heat compression bonding, heat stretching, etc. .

Next, a specific example of the present invention will be described below in which the existence of a gap having no lens effect is eliminated between rod-shaped optical elements.

FIG. 12 is a sectional view of a glass rod 17 having a square cross section, which is obtained by grinding the side surface of a thick glass rod having a refractive index distribution.

FIG. 13 is a sectional view of a glass rod 18 having a regular hexagonal cross section, which is obtained by grinding the side surface of a thick glass rod having a refractive index distribution.

By covering the side surfaces of such glass rods 17 and 18 with light absorbers and subjecting them to heating and stretching treatment as shown in FIG. 2 or FIG. 9, collective type gradient index optical elements and A large-area collective gradient index optical element can be manufactured.

The present invention has been described above based on various specific examples.

In addition, when the refractive index distribution of the glass rod material used in the present invention is formed by ion exchange treatment, the ion exchange treatment time is slightly shorter than usual, and the ions are thermally diffused by the subsequent heating and stretching process. It is preferable to use a method that creates an optimal distribution of refractive index.

Moreover, the light absorber used in the present invention may not only cover a glass rod material that already has a refractive index distribution, but also may form a refractive index distribution after covering the glass rod material with the light absorber. For example, when forming a refractive index distribution by ion exchange treatment, if the coefficient of thermal expansion of the light absorber is made smaller than that of the outer periphery of the glass rod, after the heating and stretching process, the crimping effect will cause the individual glass rods to This has the effect of improving the strength of the material and making it difficult for the collective type gradient index optical element to suffer from breakage defects.

〔Effect of the invention〕

As explained above, according to the present invention, a compact collective gradient index optical element with a short conjugate length made of a glass rod material having a small diameter and a large distribution of refractive index differences in the radial direction can be easily produced. can be manufactured. Furthermore, if necessary, the gap is filled with a second light absorber, a flexible sheet-like material, a lens-effect-free material with no voids, or a large-area aggregated refractive index distribution optical material. Elements etc. can be easily manufactured.

(Example〕 Hereinafter, the present invention will be explained in more detail with reference to Examples.

Diameter 3 made of borosilicate glass containing 20 mol% Li20
A cylindrical member with a length of 100 cm and a length of 100 cm was immersed in a molten salt of sodium nitrate kept at 500° C. for 100 hours to perform ion exchange and form a refractive index distribution in the member.

Next, the 19 members were bundled into a regular hexagonal shape as shown in Figure 2, and heated in an electric furnace maintained at 640°C.
2700m by tension roller while feeding at 7 minutes
It was stretched at 1/min. Then each member has a diameter of approximately 0. ]I
I+m, and were fused to each other in a regular hexagonal shape. The aggregate thus obtained was cut at intervals of 3m+s,
Furthermore, the cut surface was polished to produce multi-fibers.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional method for manufacturing a collective type gradient index optical element, FIGS. 2 and 9 are schematic diagrams showing an example of the heating stretching process of the present invention, and FIGS. 5, 7 and 1O are cross-sectional views of an aggregate type gradient index optical element manufactured according to the present invention, FIG. 6 is a cross-sectional view of an aggregate of glass rods having a refractive index distribution, and FIG. 11 is a schematic cross-sectional view of a large-area collective-type gradient index optical element, FIG. 11 is a cross-sectional view of a drum winding up the collective-type gradient index optical element, and FIGS. 12 and 13 are those whose sides have been ground. It is a sectional view of a glass rod material. 1.4a, 4b --Glass rod material, 2---------Spacer, 3------
Plate materials, 5a, 13a, 15a--one assembly, 5b, 9, 11, 13b, 15b--one assembly type gradient index optical element, 6---Heating furnace, 7--・-Tension roller 8---------Light absorber, 10
--- ISA absorber 12a, 12b =-2nd
Light absorber, 14--------Large-area collective type gradient index optical element 1B--One winding drum, 17.18--One ground glass rod Material. Mo1 Figure 4b Funeral Figure 2 Figure 3 Octopus Figure 6 Copper Figure 7 Figure 8 Figure 9

Claims (5)

[Claims] (1) In a method for manufacturing a collective type gradient index optical element in which glass rods having a refractive index distribution are bundled and fixed, a plurality of glass rods having a refractive index distribution are bundled and stretched by heating. 1. A method for manufacturing a collective graded refractive index optical element, the method comprising the step of fusing rods together. (2) A patent in which the refractive index distribution of the glass rod is formed by immersing the glass rod in a molten salt and exchanging ions in the glass rod with ions in the molten salt. A method for manufacturing a collective graded index optical element according to claim 1. (3) Collective refractive index gradient optics according to claim 1 or 2, which includes the step of further bundling and bonding a plurality of aggregates made of a plurality of glass rod materials fused by the heating and stretching. Method of manufacturing elements. (4) Aggregated refractive index distribution according to claim 1 or 2, including the step of further bundling and heat-pressing a plurality of aggregates made of a plurality of glass rods fused by the heating and drawing. A method for manufacturing an optical element. (5) The method for manufacturing a collective gradient index optical element according to any one of claims 1 to 4, wherein a light absorber is provided around the glass rod material.