RU2101238C1 - Glass for making gradient image translator by ion exchange method - Google Patents

Abstract

FIELD: glass industry. SUBSTANCE: glass has, mol.%: silicon oxide (SiO₂) 56-63; lithium oxide (SiO₂) 10-16; sodium oxide (Na₂O) 10-12; zirconium oxide (ZrO₂) 8-11; antimony oxide (Sb₂O₃) 0.1-0.5; R'O 2-5 where R' - Mg, Ca, Zn, Ba, Sr, Pb; R''O 0.5-3 where R'' - La, Ge, Ti, Ta, Nb, W. Properties: glass refraction coefficient is 1.52-1.61, treatment temperature in sodium salt melt is 580-700 C. Glass is used for making rigid medicinal endoscope by method of ion-exchange diffusion. EFFECT: improved quality of glass. 2 tbl

Description

 The invention relates to the glass industry and optical engineering, more specifically to the compositions of optical glasses intended for the manufacture by ion exchange diffusion in molten salts of gradient image translators for rigid medical endoscopes.

 A known composition of glass for the manufacture of optical fibers by ion processing of billets from it in molten salts. The specified glass contains the following components, wt.

SiO ₂ 11.3 56.8;
B ₂ O ₃ 9.4 17.4;
Al ₂ O ₃ 4.8 5.1;
Li ₂ O 2.3 7.1;
Na ₂ O 0.8 5.1;
As ₂ O ₃ 0.5 0.6;
GeO ₂ 15.8 65.7.

The glass is boiled at 1450 ^o C. Cylindrical semi-finished products are obtained from the finished glass, which are then subjected to high-temperature ion exchange - processing in a molten sodium nitrate salt at a temperature of 550 ^o C for 100 hours. The resulting optical fibers (gradient image translators) thus obtained have a difference refraction from the axis to the surface of the element "Δn" from 0.006 to 0.01 with a refractive index of 1.50 1.63. With an image translator length of 60 mm, it has a resolution of 200 lines / mm. RMS wave aberration Δ = 0.15 λ. The maximum wave aberration D _m = 0.4 λ where λ is the average wavelength of visible light 550 nm.

However, the invention has several significant disadvantages. The main one is the relatively short length of the translator, not exceeding 60 mm. Attempts to increase the length of the translator to 100 mm or more lead to a sharp deterioration in image quality, since aberrations increase to the following values: D> 0.25 λ, Δ _m > 0.9 λ. At this level of aberrations, the image becomes difficult to distinguish.

 By technical nature and the achieved effect closest to the claimed invention relates to a prototype.

 The composition of glass used for the manufacture of elements by ion exchange includes the following components, mol.

SiO ₂ 60 78
Li ₂ O 2 24
Na ₂ O 6 16
ZrO ₂ 5 13
Sb ₂ O ₃ 0.1 1.0
NaCl 2 5
GeO ₂ 0.1 0.5
Glass is boiled in an oven in quartz containers with a volume of 8 l installed in a fireclay vessel. Cooking and clarification is carried out at 1500-1550 ^o C.

From the obtained glass, preforms of translators with a diameter of up to 16 mm are made, which are then processed in a melt of sodium salts, for example NaCl + Na ₂ SO ₄ at a temperature of 670-700 ^o C for 2-5 hours

 The result is a gradient image translator, which is a glass cylinder with a diameter of up to 16 mm and a length of 100 mm.

The level of rms wave aberration in this case is: Δ = 0.1 λ maximum D _m = 0.4 λ Resolution of the translator does not exceed 200 lines / mm. The refractive index n is 1.59, with its difference from the axis to the surface of the element: Δn 0.007.

Целью предлагаемого изобретения является получение стекла, которое позволяет изготовить из него повышенной длины градиентные трансляторы с высоким качеством изображения.However, the invention also has a number of significant disadvantages. So, for example, a gradient image translator has a relatively short length not exceeding 100 120 mm. With an increase in translator length of more than 150 mm, the image is almost indistinguishable due to high aberrations:

The aim of the invention is to obtain glass, which makes it possible to produce gradient length translators with high image quality from it.

The goal is achieved by the fact that to the known composition of glass, including oxides of silicon, lithium, sodium, zirconium, antimony, make structural and technological additive containing one or more metal oxides taken from the series: MgO; BaO; CaO; ZnO; SrO; PbO, as well as simultaneously one or more metal oxides from the series La ₂ O ₃ ; GeO ₂ ; TiO ₂ ; Ta ₂ O ₅ ; Nb ₂ O ₅ ; Wo ₃ .

The essence of the invention lies in the fact that our first additive allows us to reduce the temperature of glass melting and to carry out the process at a temperature not exceeding 1450 ^o C. Therefore, the additive is called "technological". On the other hand, the introduction of metal oxides included in the second additive allows you to change the structure of the glass. A change in the structure of glass is reflected in the optical and ion-exchange properties of image translators. Therefore, the additive we have proposed is also called "structural." We found and experimentally confirmed that the amount of the additive, as well as the metal oxides included in the additive, allows to obtain the optimal optical properties of image translators, despite the dependence of their optical properties on the length of the translator.

где λ средняя длина волны видимого света 550 нм.It is known that high image quality is achieved if the maximum wave aberration Δ _m satisfies the Rayleigh criterion:

where λ is the average wavelength of visible light 550 nm.

As another criterion for high image quality, the mean square wave aberration “D” is used. It must satisfy the following criterion: D ≤ 0.07 λ
Our proposed structural and technological additive allows us to produce image translators with a length of 150-400 mm with a sharp reduction in aberrations compared to the prototype, i.e. with high image quality with maximum translator lengths.

 The following examples illustrate the invention.

Example 1. (table. 1) The experimental glass was boiled in a platinum vessel with a capacity of 6 liters in a furnace with an electric heater at a clarification temperature of glass mass of 1430 ^o C. The mixture contained the following ingredients in mol.

SiO ₂ 60.0
ZrO ₂ 10.5
Li ₂ O 10.5
Na ₂ O 12.5
Sb ₂ O ₃ 0.5
and structural and technological additive mol.

CaO 2.0
PbO 1.5
La ₂ O ₃ 2.5
The following reagents were used in the preparation of the charge: amorphous silica, zirconia, lithium carbonate, sodium carbonate, calcium carbonate, lead nitrate, antimony trioxide, lanthanum trioxide.

Cylinders with a diameter of 0.8 mm and a length of 200 mm were made from the obtained glass, which were then processed in a mixture of lithium and sodium salts at a temperature of 610 ^o C. As a result, a gradient image translator was obtained, the optical properties of which are given in Table. 2.

 Example 2-6. In the conditions of example 1 obtained glass, the composition of which is given in table. 1. On the basis of 2 6 glasses prepared in experiments, gradient image translators were made, the parameters and optical properties of which are given in Table. 2.

 Example 7. In the conditions of the prototype made glass in the following ratio of components, mol.

SiO ₂ 60.0
Li ₂ O 14.0
Na ₂ O 12.5
ZrO ₂ 10.0
Sb ₂ O ₃ 1.0
NaCl 2.0
CeO ₂ 0.5
The cooking process proceeded at 1550 ^o C. Translator blanks were made from the obtained glass, which were then processed in a molten salt of Na ₂ SO ₄ + NaCl at 690 ^o C for 2 hours. The diameter of the blanks was 3 mm, length 80 mm and 300 mm. The parameters and optical properties of gradient image translators are given in table. 2.

 Example 8. Under the conditions of example 7, glass was made in the following ratio of components, mol.

SiO ₂ 78.0
Li ₂ O 5.4
Na ₂ O 6.0
ZrO ₂ 5.0
Sb ₂ O ₃ 0.1
NaCl 5.0
CeO ₂ 0.5
The cooking process proceeded at 1500 ^o C. The diameter of the translator blank was 3 mm with a length of 40 and 200 mm. The workpieces were processed in a molten salt of Na ₂ SO ₄ + NaCl for 2.5 hours at 700 ^o C. The parameters and optical properties of the finished gradient image translators are given in table. 2.

From the data presented in table. 1 and 2, it can be seen that based on the glass known in the prior art, translators (op. 7 and 8) were made, the length of which was 80; 300; 40 and 200 mm (tab. 2, item 3). From the data of paragraph 4 of the table. 2 shows that with a translator length of 80 and 40 mm, the image quality is satisfactory D _m 0.30 and 0.5, respectively. This follows from paragraph 5 of this table, which characterizes the wave mean-square aberration, which should be: Δ ≤ 0.07 λ. However, when trying to increase the length of the translators obtained under the conditions of the prototype, up to 300-200 mm, the image practically does not differ, and D = 0 , 35-1.2 λ and Δ _m = 0.8-4.0 λ, respectively.

Experiments 1-6 indicate that when using one or more metal oxides as our proposed additives from the series: MgO, CaO, ZnO, BaO, SrO in an amount of 2 ^o C 5 mol. and at the same time one or more metal oxides from the series La ₂ O ₃ ; GeO ₂ ; TiO ₂ ; Ta ₂ O ₅ ; Nb ₂ O ₅ ; WO ₃ in an amount of 0.5 to 3 mol. it is possible to achieve the goal: to obtain gradient translators with high image quality and high resolution (more than 200 lines / mm), with Δ _m = 0.15-0.25 λ and Δ = 0.04-0.07 λ and the length of the translators within 200 400 mm. So, for example, in op. 5, the translator length is 300 mm with a thickness of 2.5 mm, Δ = 0.06 λ and a resolution of 300 lines / mm. The resolution (image quality) of the translator in op.5 exceeds the image quality for translators from op. 7 to 7 times.

The use of metal oxides from the series MgO, CaO. PbO in a concentration of less than 2% (mol.) Does not allow to reduce the temperature of glass melting to 1450 ^o C and below. The use of these oxides in an amount greater than 5 mol. does not give a positive effect.

The use of metal oxides from the series La ₂ O ₃ , WO ₃ in an amount of less than 0.5 mol. virtually no effect on the change in the optical properties of the translators. Their use in quantities greater than 3 mol. negatively affects the optical properties of the translators, their cost increases. The optimal concentration range for metal oxides taken in the form of one or more oxides from the series: MgO, CaO. PbO is in the range of 2 to 5 mol.

The optimal range of concentrations of metal oxides taken in the form of one or more oxides from the series: La ₂ O ₃ ; GeO ₂ ; TiO ₂ ; WO ₃ is in the range of 0.5 to 3 mol.

 The introduction of the specified structural and technological additives in the glass composition at the indicated optimal concentrations allowed us to achieve our goal: to obtain gradient image translators of the required length with high image quality.

 Our glass composition for obtaining gradient image translators does not require increased energy costs at the stage of glass melting and its processing in molten salts. A positive economic effect is achieved when selling medical endoscopes using translators made on the basis of the proposed glass formulation and providing high quality images of the organ under study from any depth in the patient’s body.

Claims (1)

Glass for the manufacture of gradient image translators by ion exchange, including SiO ₂ , Li ₂ O, Na ₂ O, ZrO ₂ , Sb ₂ O ₃ , characterized in that it additionally contains one or more metal oxides R ^' and one or more metal oxides R ^'' O in the following ratio of components, wt. SiO ₂ 56 63
Li ₂ O 10 13
Na ₂ O 10 12
ZrO ₂ 8 11
Sb ₂ O ₃ 0.1 0.5
R ^' O, where R ^' Mg, Ca, Zn, Ba, Sr, Pb 2 5
R ^'' O, where R ^'' La, Ge, Ti, Ta, Nb, W 0.5 3.0 s

Images