JPS5954631A - Preparation of lens having refractive index distribution in axial direction - Google Patents

Abstract

PURPOSE:To prepare a lens having extremely low aberration on the axis, by attaching fine particles of glass on the surface of a starting substrate with changing a dopant concentration in the normal direction, growing it, making it transparent, processing end faces into a spherical surface with aligning an axial line with the direction of refractive index distribution. CONSTITUTION:A glass-forming raw material gas such as SiCl4, etc. supported on a carrier gas such as Ar, etc. is fed from the feed pipe 11 to the torch 10 made of quartz glass, a combustible gas such as H2, etc. is fed from the feed pipe 12 to it, the glass- forming fine particles 13 are formed by a flame hydrolysis reaction, and the soot layer 15 is grown on the substrate 14. In the growth, the soot layer 15 having a composition distribution in the thickness direction is formed by changing continuously a feed concentration of the soot 13. The soot layer 15 is heated at high temperature in an inert gas, and processed into the transparent plate 16 having a refractive index distribution in the thickness direction. The glass plate is ground and polished in such a way that the face 16A with low refractive index of the glass plate 16 is a plane, the face 16B having high refractive index has a given radius R of carvature, and the center of the curvature is positioned on the normal of the glass 16, to give the lens 17 having refractive index changing successively in the optical axis.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a spherical lens in which the refractive index changes continuously in the light 1q11 direction, and the refractive index is bimodal within a plane IU perpendicular to the light 1111+. .

Spherical lenses with a uniform refractive index, which are generally used in optical lenses, have relatively large aberrations, for example, the lens thickness at center C is 7'mm and the radius of curvature is 7.2mm'.

According to the optical ray meter nK, the axial aberration of the plano-convex lens has a maximum value of about 7.7 mm, as shown in the graph of the refractive index/.

This axial aberration can be improved by selecting the lens thickness, radius of curvature, refractive index, etc., but unless the lens thickness and radius of curvature are made considerably smaller, the axial aberration will be several hundred microns. It is safe to say that it is almost impossible to obtain a lens with small aberrations.

Furthermore, in order to solve the above-mentioned drawbacks of spherical lenses, a method has been proposed in which a low-aberration lens is created by processing an aspheric surface, but this method has the disadvantage that processing is more difficult than that of a spherical lens.

As a lens that solves the problem described in item 2, one side is spherical and the other side is flat, and inside a plano-convex lens, there is a point VC at a distance of Z in the optical axis direction from the lens surface. Let r+(Z) be the refractive index at the center of the spherical surface as η0.

n (Z)-ηof, (Z) ・・・・・・zo/)
・ ・A lens has been proposed that is continuously curved as shown by □ and has a refraction □ and index distribution such that the optical axis has a uniform 1i11 refraction rate within the 71 pieces. There is C.

For example, as shown in the diagram, in a plano-convex lens 1111 where one lens surface / is spherical and the other lens surface 2 is flat, the refractive index NO
The maximum value is 7, and the refractive index decreases continuously in the thickness direction toward the flat lens curve.
Let us consider l11111'i index distribution such that the IFil refractive index is uniform within any n1r iT+i 4'. nikarashi” (ray S parallel to the optical axis
is incident, the larger the distance Z between the lens surface/center and the 41 plane l perpendicular to the optical axis passing through this point of incidence, the greater the human ra.
Since the refractive index at point t gradually decreases, the refractive index of the lens ((compared to
The angle of refraction of a ray of light that is 1 is relatively steep.

As a result, as shown by the broken line in the figure, the axial aberration unique to the spherical lens, in which the rays incident at a position far from the optical axis are focused at a position closer to the lens surface 6 than the near 11111 rays, is corrected. As a result, a lens with extremely low aberrations can be obtained.

[41] As a method for manufacturing a glass plate for such an axially distributed index lens, a method has been proposed in which a refractive index distribution is created in the thickness direction by an alkali ion exchange method of alkali-containing glass. Since it utilizes a type of diffusion phenomenon called exchange, the refractive index distribution cannot be controlled arbitrarily, and if the refractive index difference △n is reduced to a large value,
At the same time, the difference in the expansion coefficients of the 1S Δ glass plate after the glass plate is replaced also increases, leading to problems such as easy breakage.

It is an object of the present invention to provide a novel method for manufacturing an axially graded refractive index lens that solves the second problem.

In the method according to the present invention, a glass-forming raw material gas is supplied to a glass particle synthesis torch, and 5
1) If glass particles containing i02 as a main component and dopane 1 for adjusting the refractive index are produced, the concentration of the dopant is changed in the direction normal to the face of the starting substrate. After the glass layer is grown, this is heated at high temperature to make it transparent to create a plate-shaped lens whose refractive index changes continuously in the thickness direction, and then After this one-width glass plate is cut into small plates as necessary, at least one end surface is made into a spherical surface with the refractive index distribution direction set to the 4q11 line.

'' - If the direction θ is J: then the refractive index distribution in the thickness direction can be freely selected, and the lens thickness can be freely adjusted lβ.

Furthermore, by adding VC to the glass using Tj-02 as one of the dopants along with other oxides, the stress generated in the glass can be reduced.

The method of the present invention makes it possible to easily create a spherical lens with minimal axial aberrations.

1. The present invention will be explained based on the drawings.

First of all, figure 1 (a) shows the synthesis of glass microparticles made of multiple tubes made of glass or metal.
Chi10 KSiCla, GeG14. Ti(J+, P
A glass-forming raw material gas such as O
A combustible gas and a combustion assisting gas such as 2+02 are supplied to the synthesis torch 10 through the other supply pipe/2 to form glass-forming fine particles (hereinafter referred to as 1) by a flame hydrolysis reaction.
A soot layer 15 is grown on a plate-shaped substrate such as graphite or quartz glass provided in front of the torch 10.

At this time, by continuously changing the supply concentration of the glass-forming raw material gas, a soot layer/layer having a composition distribution in the thickness direction can be obtained. At this time, in addition to the above-mentioned gold halide, an atomized aqueous solution of an organometallic compound or a metal salt may be supplied as the target area and glass forming raw material gas. By heating the deposited soot layer/layer at high temperature in an inert gas of ne + Ar qη, it is bent in the thickness direction. A transparent glass lower plate/B was prepared to improve the rate distribution.
The glazier/plate serving as the glass material may be wet-heated in an atmosphere of 5OC42 or the like.

Next, this 1V thin glass plate/B is divided into small plates of a predetermined size or cut as is, and the low refraction of the glass plate 7B is calculated.
i'iK fJf Polishing 1: Along with I' 1-71, the high refractive index surface IIB side is polished to a predetermined radius of curvature R-CL1. Place the center of curvature on the normal line -1- of the glass plate/B.ii'j
Sharpen C11t, 6) [Polish.

In this way, KL has low refractive index/7A with 11 planes and high hI.
(The refractive index surface /7B is a spherical surface.) It is possible to manufacture a lens /7 whose refractive index changes continuously in the optical axis direction.

-Example 1-The refractive index N at the center of the spherical lens surface /'7]3 (1=/, , B, from the maximum refractive index point to the lens d) The refractive index J that falls at a distance Z in the thickness direction ? rate n (z) to n
When expressed as (Z) -y2n</--OZ), the constant a
4 o,'=tuomn+-].

The lens thickness at the center is /'m, m, and the curvature of the lens surface is 1
'The diameter R is 3,! Evening+nm ', 3.2'jj mm
, 3. The axial aberration when Jl + mm is as shown in the graph in Figure 3. - As can be seen from this graph, the maximum value of the axial aberration can be kept within an extremely small range of plus or minus 7 μm. □In carrying out the present invention, various dopants for adjusting the refractive index can be used, but Tio2 is particularly preferred. That is, G602 lP2O5r A1.5io2 is used as a reference. g03, P
When a refractive index adjusting dopant such as bO is added, the expansion coefficient of the lens base material glass becomes larger than that of glass made of only 5i02.

Therefore, when a large amount of dopant is added to increase the difference in refractive index of the lens, the stress generated in the matrix glass makes the glass more likely to break.

In particular, when mechanical processing such as cutting or spherical processing is applied to the glass, the glass becomes chipped. By adding TiO2 with other oxides, TiO2 has the unique property of lowering the expansion coefficient of the glass compared to other oxides, resulting in a large refractive index difference and a lower expansion coefficient in the thickness direction. The difference is small and the lens base material glass can be processed and processed.

-・B2O3 is ce62 I P2O5, 'Ae2
03. Similar to □ oxides such as PbO, 5102 SoIf'
When □ is added to lath, the expansion coefficient tends to increase /l<
However, it is well known that it has the property of decreasing the refractive index.

However. In carrying out the present invention, the B2O3 doped 5i02 composition is changed to reduce the K13203 concentration in the thickness direction, and GeO2+ P2O5, Alz
03. By increasing the expansion coefficient and refractive index of PbO, etc., and increasing the concentration of oxide in the warp direction, the expansion coefficient can be decreased and the refractive index difference can be increased by 1. You can also do it.

JCJ, J: The present invention has been described with respect to manufacturing an axial gradient index lens in which the high 11.1'l refractive index surface is a spherical surface and the low refractive index surface is a flat surface. It is also possible to manufacture lenses with a spherical low refractive index surface, which are used as lenses for commercial purposes, or lenses with a low refractive index surface spherical and a high refractive index surface flat, by the method of the present invention.

[Example 1] H2 gas: toocc/min, 02 gas: 000cc/min were supplied to a torch made of quartz, and 5i was placed in the flame created.
C14 gas: Supply '300 CC/min and produce 5i02 soot through flame hydrolysis reaction! ; OX, S'Omtn size was deposited on a quartz glass substrate.

Immediately 'GeC12 and POIJ3 raw materials are increased continuously, final KSiC14;23'0.00:/min+GeO14::Otsu5CC/min,'P OC13
``The raw material concentration was changed to 30 CC/min.

Thereafter, the deposited soot layer is heated at about /11.00'C to form a layer on the quartz substrate with a thickness of about 7.5mm, in which the refractive index changes continuously in the thickness direction. A transparent glass plate of jmIn was obtained.

The refractive index distribution in the thickness direction of this transparent glass plate is such that the refractive index n (Z) at a depth ZK from the surface is 'n (Z) =
/, sy'v/-o: o4/311.2z; refractive index of high refractive index surface/, □si, low refractive index surface low refractive face',
1, the refractive index difference between the two surfaces of Oji was Δn−o,ot. □Next, the above glass plate was spherically processed so that the high refractive index surface was convex to produce an axially distributed refractive index lens with a radius of curvature of 9㎜Qmm, a lens thickness of 751 nm + a lens diameter of 9.9㎜.

When the rli+I+ upper aberration of the lens J- was measured, it was found to be less than .mu.rll within 0% of the lens diameter with respect to a light source with a wavelength of 0.times.3 .mu.n+.

〔Example! ]

In the same manner as in Example/, H2 nitrogen soo'aa/min.

02: too aci worth of flame K 5iC14
: , 10O100X100 by supplying 2JoDOAk
The first suit was placed on a quartz glass substrate with a size of .

After that, the g attachment of GeO/i'4 + Tl014 was gradually increased, and finally 5i(J4: xos GO
/min, G6cd4: 4. tCc/relaxed Tj-C14
: Adjusted to 113 CC/min. .

Thereafter, a transparent glass plate with a thickness of about 3.0 mm+ was obtained on the quartz substrate by heating the first layer of the layer "-" at about /1100"C.

The refractive index distribution in the thickness direction of this transparent glass plate is n (z
), =,, / 3g (/ -0,0/21p z>,
l, q refractive index on the refractive index surface side/, j4 + TLi′ on the low refractive index surface side! Fraction rate 8++.

It was n-0,/.

Process the high refractive index surface into a spherical surface with a radius of curvature of 6.3 mm and polish the low refractive index surface into a flat surface with A distributed lens was obtained.

The axial aberration of the lens obtained in this way is 3 μm at wavelength O9
Within the range of 0% of the lens diameter, the difference was ±gμm or less for the light beam.

[Example 3] 5iC14 was supplied to a quartz torch to generate a flame by supplying it at a rate of 200 CC/min for H2: Otsu and 000 CC/min for 02: 000 CC/min.
'JtlOCC/min, BBr3: 10OCC/min was supplied to deposit a thin soot layer on the graphite deposit of diameter/Q Om mm. After that, while gradually decreasing the supply 1i of BBr3, Ge CA 41 T 1
0 (Start adding 14 and gradually increase the amount added.)
u1 final raw material supply lit is 5i014 + /90
CC,/min, Ge01. : 2occ/min, T1a
04:jtO(A7min, 13Br3: 000/
The soot layer was allowed to grow gradually while changing the amount of the soot layer.

This soot layer was heated at about /300'C to obtain a transparent vitrified glass flat plate having a thickness of about J;mtn.

1n (refractive index distribution in the thickness direction of this transparent glass flat plate is n
<z> =1. szy/-o, o3/5tz-, refractive index of high refractive index surface/, oza, refractive index of low refractive index surface/, 4
/, lt, Δn-0, /3.

Next, the high refractive index side of the glass plate has a radius of curvature/3. )
! Polished to a spherical surface of 73 mtn, and the other surface is polished to a flat surface, with a thickness of 1" in mm and a diameter of 20. zam itφ (
llr direction, a coexisting refractive index distribution type lens was obtained.

The axial aberration of the lens thus obtained is wavelength q = 1.3t
within the range of 0% of the lens diameter for the ray of tm, j7
It was im7n.

[Brief explanation of drawings]

FIG. 7 is a graph showing an example of axial aberration in a conventional spherical lens, and the ono diagram is a cross-sectional view showing an example of an axial gradient index lens manufactured by the method of the present invention. Fig. 3 is a graph showing a numerical example of the axial difference of 1 mm for lenses manufactured by the method of the present invention, and Figs. be. l・・・・・・High refractive index surface C・・・・・・・・・
Low refractive index surface ゛3...Optical axis l...
...Uniform refractive index surface S...Light ray 10...
...Glass particle synthesis torch//...Glass raw material supply pipe/2...Fuel supply pipe/
3... Glass-forming fine particles (soot) /ll... Substrate /j... Deposited soot layer/B... Gradient index glass plate /7
・・・・・・Axial gradient index lens Figure 1
・Figure 2, Figure p. Director-General of the Ministry of Finance, Director-General of the Ministry of Finance - 2 Name of the Invention Method for Manufacturing an Axial Graded Index Lens 3 Supplementary Information (Relationship with 'l' %l! 'l' Application Address: Doshomachi Gu-chomeza, Higashi-ku, Osaka-shi, Osaka Prefecture Name (/Ioo)
E1 Hon Sheet Glass Co., Ltd. Representative Nobu Sagara 141 Hiro Agent Residence r5't Shinbashi S-chome 1-3-1, Minato-ku, Tokyo
Hashi Sumitomo Building [-1 Honsha Glass Co., Ltd. Patent Department Specification - Detailed Description of the Invention Column 1) Off Page 3rd Line of the Specification KI-This σ-〉'' and J6ruσ) [-At this Time'' and correct it. 2) Specification page 7, no OQ line, 1 Sashimi/S? TeVko[-
"Glass 51 Otsu plate/6" is replaced with "Deposited soot layer 15J"
and Supplementary J1:. 0 3) Specification O//page Og line 1-±/j III J
0 to correct a certain σ] to 1±/"7z m "'J
ln

Claims (1)

[Claims] A glass-forming raw material gas is supplied to a torch, and glass particles containing 5i02 as a main component and a dopant for adjusting the refractive index are produced by a flame hydrolysis reaction. After growing the dopant while changing the concentration of the dopant in the linear direction, it is heated at a high temperature to make it transparent. Next, after cutting this base +2 glass plate into small plates if necessary,)
Decoy 1 direction 111 (method for manufacturing a gradient index lens) characterized in that at least the end face on the −· side is processed into a spherical surface for the r-ray.