CN115959827A - Gradient-refractive-index infrared chalcogenide glass lens and preparation method thereof - Google Patents
Gradient-refractive-index infrared chalcogenide glass lens and preparation method thereof Download PDFInfo
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Abstract
The invention discloses an infrared chalcogenide glass lens with gradient refractive index, which is prepared by sequentially stacking a plurality of basic samples with flat surfaces and different components according to the refractive index and performing precision compression molding, wherein the molar composition of each basic sample is expressed As As according to the chemical formula 40 S (60‑x) Se x Wherein x is more than or equal to 0 and less than or equal to 60. The gradient refractive index infrared chalcogenide glass lens can realize larger refractive index changeAnd the maximum refractive index span delta n at a 10-micron waveband can reach 0.48, the transmittance is good at a 2.5-12.5-micron waveband, and the infrared thermal imager has excellent application prospects in miniaturization, light weight and high performance. The preparation method of the gradient-refractive-index infrared chalcogenide glass lens can ensure that the refractive index configuration of the gradient-refractive-index infrared chalcogenide glass has stronger repeatability, and the infrared chalcogenide glass lens with the gradient refractive index of a plane or a curved surface can be directly pressed.
Description
Technical Field
The invention belongs to the technical field of infrared glass materials, and particularly relates to an infrared chalcogenide glass lens with a gradient refractive index and a preparation method thereof.
Background
It is well known that infrared lens materials are one of the bases for the development of infrared thermal imaging systems. In recent years, with the rapid development of infrared technology, the application of infrared thermal imaging systems is more and more extensive. Meanwhile, the wide application also brings new challenges to the development of the infrared thermal imaging system. Diversified applications require that the system must be suitable for various extremely complex environments, such as portable weapon systems, unmanned aerial vehicles, and the like, which requires that the infrared optical imaging system be developed towards miniaturization and light weight, and simultaneously requires that the imaging quality be balanced. However, the slow development of infrared optical lens materials has restricted the development of infrared optical systems to some extent. Mainly because with the reduction of the size of the infrared focal plane array pixel, the deviation of the optical imaging component generated in the modulation is difficult to break through the optical diffraction limit. Therefore, the development of new infrared lens materials is required to be accelerated, and the targets of miniaturization, light weight and high imaging quality are achieved by combining with infrared optical design.
Gradient index (GRIN) lenses have a non-uniform distribution of spatial refractive index that varies gradually along a direction. And can be roughly divided into axial, radial, spherical and other gradient refractive index profiles. Compared with the traditional lens, the gradient refractive index lens can effectively correct aberration and chromatic aberration, one gradient refractive index lens can achieve the effect of combining a plurality of traditional lenses, and the miniaturization and lightweight development of an optical system are promoted. Commercial gradient index lenses are mainly focused on visible wave bands, mainly adopt an ion exchange method, and no commercial infrared gradient index lens material is available in the market. The existing infrared optical imaging system is difficult to simultaneously consider the volume and the imaging quality, so that the development of an infrared gradient refractive index lens material is urgently needed.
The commonly used infrared lens materials mainly comprise crystal materials such as Ge, znSe, znS and the like and chalcogenide glass. Although the infrared crystal material has better infrared optical performance, the intrinsic property of the crystal makes the subsequent treatment difficult to achieve the purpose of regulating and controlling the refractive index distribution. Chalcogenide glass is considered to be an excellent material for infrared optical systems because of its good infrared transmission properties, continuously adjustable components, and ease of processing. At present, the infrared chalcogenide glass with gradient refractive index can be prepared by adjusting the component design and subsequent processing treatment.
The existing preparation methods of the infrared chalcogenide glass with the gradient refractive index can be mainly divided into three categories. The ion exchange method, the gradient crystallization method, and the stack diffusion method can be classified according to the cause of the gradient refractive index.
The ion exchange method is to introduce movable ions into chalcogenide glass and to place a sample in a heated salt bath solution of different ions for ion exchange. The radial gradient refractive index gradual change can be realized by an ion exchange method, but the greatest defect is that the gradient distribution of ions can be realized only by soaking for dozens of days, the refractive change range is very limited, and the application requirement of an infrared optical system cannot be met.
The gradual crystallization method mainly includes precipitating a crystal in chalcogenide glass, and forming a gradual crystal distribution in the glass through a gradual temperature field due to the difference between the refractive index of the crystal and the refractive index of a glass matrix, so as to obtain a gradient refractive index, which can be specifically referred to chinese patent application No. 201710579672.6. Theoretically, the purpose of adjusting the refractive index distribution can be achieved by controlling the size and the number distribution of crystals, but the greatest difficulty is how to perform fine glass controlled crystallization. In addition, a plurality of crystals can be separated out after the substrate glass is subjected to heat treatment, the crystals can be nested with one another, and the difficulty is how to ensure uniform gradual change of the spacing between the crystals.
The stack diffusion method mainly comprises grinding two kinds of glass with different components into powder, mixing the powder according to different proportions, flatly paving the powder layer by layer, carrying out hot press molding, and carrying out heat treatment on a sample after hot press, and can be specifically referred to Chinese patent with application number of 202111520507.6. The method is to regulate the size of the refractive index by using glass powder with different proportions. The method mainly has the following difficulties: firstly, how to fully and uniformly mix glass powder with different components, if the glass components are not uniformly mixed, irregular refractive index change appears on the same plane after hot pressing; secondly, how to press glass powder layers with different proportions into the same density, if the density of the same layer is different, the refractive index of the same layer is different; then, how to ensure the surface smoothness and thickness uniformity of each layer, the non-uniform surface or non-uniform thickness of each layer may cause unnecessary scattering at the interface of the two layers, which may ultimately affect the predetermined gradient refractive index structure, and the repeatability is difficult to control.
Disclosure of Invention
The technical problem to be solved by the invention is to provide the gradient-refractive-index infrared chalcogenide glass lens and the preparation method thereof, the lens can realize larger refractive index change, the maximum refractive index span delta n at the 10 mu m wave band can reach 0.48, and the lens has excellent application prospect in a miniaturized, light-weighted and high-performance thermal infrared imager.
The technical scheme adopted by the invention for solving the first technical problem is as follows: the gradient-index infrared chalcogenide glass lens is composed of multiple flat surfacesDifferent basic samples are sequentially stacked according to the refractive index and are prepared by precision compression molding, and the molar composition of each basic sample is expressed As As according to the chemical formula 40 S (60-x) Se x Wherein x is more than or equal to 0 and less than or equal to 60.
The invention selects As with excellent thermal stability 40 S (60-x) Se x The glass component is used as a basic sample, so that the infrared transmittance is not influenced by crystallization in subsequent treatment, the transmittance is good in a 2.5-12.5 mu m wave band, and the refractive index change of the obtained lens is good in controllability. According to the requirements of the infrared optical system design on the gradient refractive index structure, different components and the same thickness or different thickness combinations of a plurality of basic samples can be designed, and the infrared chalcogenide glass lenses with different surface types and gradient refractive index distributions can be obtained by utilizing the precision compression molding technology. The gradient-refractive-index infrared chalcogenide glass lens can realize larger refractive index change, the maximum refractive index span delta n at the 10 mu m wave band can reach 0.48, and the gradient-refractive-index infrared chalcogenide glass lens has excellent application prospect in a miniaturized, light-weighted and high-performance thermal infrared imager.
Preferably, the chemical formula is As 40 S (60-x) Se x The difference between the maximum glass transition temperature and the minimum glass transition temperature of the glass composition of (2) is less than or equal to 30 ℃.
The preparation method of the gradient-refractive-index infrared chalcogenide glass lens comprises the following steps of:
(1) Determining the components of each base sample, and preparing slices for different components of the base sample according to the following methods respectively: according to the formula As 40 S (60-x) Se x Calculating and weighing each simple substance raw material, and sequentially filling the raw materials into a quartz tube for vacuumizing to ensure that the vacuum degree in the quartz tube is less than 10 -3 Pa, then sealing the quartz tube by using acetylene-oxygen flame; putting the sealed quartz tube into a swinging furnace, heating to 750-850 ℃ for 10-12h, swinging for 8-25h, discharging, cooling by water cooling, putting into an annealing furnace at 160-170 ℃, preserving heat for 2h, naturally cooling to room temperature, removing the wall to obtain a glass columnThen, respectively slicing, grinding and polishing the glass columns into slices;
(2) Sequentially stacking a plurality of processed base sample sheets in order according to the refractive index, placing the base sample sheets on a lower molding surface of a mold in a mold pressing cabin of a precision mold pressing machine, closing the mold pressing cabin, filling nitrogen, and then lifting the lower molding surface of the mold until the upper surface of the uppermost base sample sheet is flush with the bottom surface of the upper molding surface of the mold in the mold pressing cabin;
(3) Heating the upper mold surface and the lower mold surface for the first time, and rapidly heating the upper mold surface and the lower mold surface to 160-185 ℃ respectively;
(4) Heating the upper mold surface and the lower mold surface of the mold for the second time, slowly raising the temperature of the upper mold surface of the mold to be 10-50 ℃ higher than the softening temperature of the uppermost base sample sheet, slowly raising the temperature of the lower mold surface of the mold to be 10-50 ℃ higher than the softening temperature of the lowermost base sample sheet, preserving the heat for 200-400 seconds to soften the base sample sheets, keeping the temperatures of the upper mold surface and the lower mold surface unchanged, slowly raising the lower mold surface of the mold, gradually pressurizing the softened base sample to a certain pressure, and pressing at constant temperature until the distance between the upper mold surface and the lower mold surface of the mold reaches a preset target distance;
(5) Keeping the positions of the upper mold surface and the lower mold surface unchanged, controlling the nitrogen purging speed, slowly cooling, and simultaneously and slowly cooling the temperatures of the upper mold surface and the lower mold surface to 100-130 ℃; then accelerating the nitrogen purging speed, rapidly cooling, and stopping introducing nitrogen when the upper mold surface and the lower mold surface of the mold are rapidly cooled to room temperature simultaneously;
(6) And opening the mold ballast to enable the lower mold surface of the mold to descend so as to release the pressure, taking out the infrared chalcogenide glass sample with the gradient refractive index and polishing the infrared chalcogenide glass sample to obtain the infrared chalcogenide glass lens with the gradient refractive index.
The preparation method of the gradient-refractive-index infrared chalcogenide glass lens adopts a melting quenching method to prepare the glass column, and can ensure that the interior of the glass is uniform and flawless. In the process of precision compression molding, the glass is heated for the first time to be quickly heated to the temperature near the glass conversion temperature, and the glass is heated for the second time to be slowly heated to the temperature above the glass softening temperature, so that the glass can reach the proper softening degree required by the compression molding on the premise of not generating cracks. The glass is slowly cooled to a temperature near the glass conversion temperature for the first time and is rapidly cooled to room temperature for the second time, so that the condition that the glass is cracked due to overlarge stress can be avoided on the premise of ensuring rapid forming of the glass.
Preferably, the heating rate of the upper mold surface and the lower mold surface in the step (3) is 50-100 ℃/min; in the step (4), the heating rate of the upper mold surface and the lower mold surface is 5-10 ℃/min; the cooling rate of slow cooling in the step (5) is 5-20 ℃/min, and the cooling rate of rapid cooling is 40-80 ℃/min. The heating at two rates can avoid the cracking of the glass caused by the thermal expansion of the glass due to the excessively fast heating. The adoption of two speed cooling can avoid the cracking caused by the overlarge internal stress of the glass due to the overhigh cooling.
Preferably, in the step (2), when the upper surface of the uppermost base sample sheet is flush with the bottom surface of the upper mold surface in the molding chamber, the distance between the upper mold surface and the lower mold surface is defined as the initial distance S 0 (ii) a After the pressurization in the step (4) is finished, the distance between the upper mold surface and the lower mold surface is recorded as S 1 Then S is 1 ＝40-80％S 0 . Suitable S 0 The value can ensure that heat can be transferred to the glass relatively controllably to ensure that the degree of softening of the glass is controllable. By S 1 The adjustment of the value can regulate the thickness of each layer, so that the refractive index distribution is controllable.
Preferably, the pressure during the constant-temperature pressing in the step (4) is 0.2-0.8kN. During the molding process, the proper pressure can avoid fracturing and gaps between layers.
Preferably, the upper mold surface and the lower mold surface are planar molds or curved molds, so that the infrared chalcogenide glass lenses with the planar gradient refractive index or the infrared chalcogenide glass lenses with the curved gradient refractive index can be prepared according to different requirements.
Compared with the prior art, the invention has the following advantages:
(1) The gradient refractive index disclosed in the inventionInfrared chalcogenide glass lens with molar composition As 40 S (60-x) Se x Wherein x is more than or equal to 0 and less than or equal to 60, the series of glasses are positioned in the middle part of the As-S-Se glass forming area, have excellent glass forming capability and are not easy to crystallize, the infrared transmittance is not influenced by crystallization in subsequent treatment, the change of the refractive index of the obtained lens is ensured to have good controllability, and the refractive index gradual change result is more accurate and stable.
(2) The invention discloses an infrared chalcogenide glass lens with gradient refractive index, which adopts molar composition As 40 S (60-x) Se x Wherein x is more than or equal to 0 and less than or equal to 60, the gradient-refractive-index infrared chalcogenide glass lens can realize larger refractive index change, the maximum refractive index span delta n at a 10 mu m wave band can reach 0.48, and the lens has good transmittance at a 2.5-12.5 mu m wave band, and has excellent application prospect in a miniaturized, light-weighted and high-performance infrared thermal imager.
(3) The preparation method of the gradient-refractive-index infrared chalcogenide glass lens disclosed by the invention has two advantages: firstly, the uniformity of each layer of sample can be ensured, and the refractive indexes are consistent in the same plane, so that the refractive index configuration of the gradient refractive index infrared chalcogenide glass is ensured to have stronger repeatability; and secondly, the usable plane gradient refractive index infrared chalcogenide glass lens can be directly pressed by adopting a plane mould, and the usable curved gradient refractive index infrared chalcogenide glass lens can be directly pressed by adopting a curved mould. The shape of the lens can be arbitrarily changed by changing the shape of the pressed mold.
(4) The method for preparing the gradient-refractive-index infrared chalcogenide glass lens has higher processing efficiency than diamond turning and low processing cost when the GRIN lens is prepared by adopting a precise mould pressing method. The design of the mould pressing mould can realize the diversification of the surface morphology of the lens, and the preparation process is formed in one step.
(5) The invention discloses a preparation method of gradient-refractive-index infrared chalcogenide glass lenses, and GRIN lenses with step-type refractive index distribution prepared by the method have short preparation time and industrial value. Because the method does not need element diffusion to realize the gradient change of the refractive index, the essence is that a plurality of layers of glass sheets with similar components are perfectly jointed into a whole, the glass of different layers has different refractive indexes, and the continuous change of the refractive indexes can be kept due to the similar components.
Drawings
FIG. 1 is a flow chart of the molding process of the precision molding press according to examples 1 to 4;
FIG. 2 is a schematic view of the process of molding 11 base samples of example 1 into a flat gradient index infrared chalcogenide glass lens;
FIG. 3 is a schematic view of the process of molding 11 base samples of example 2 into curved gradient index infrared chalcogenide glass lenses;
FIG. 4 is a graph of the refractive index profile of the gradient index infrared chalcogenide glass lens of example 1 (where the inset is a photograph of a cross-section of the sample).
Detailed Description
The invention is described in further detail below with reference to the accompanying examples.
Example 1: the preparation method comprises the following steps of preparing a plane gradient-refractive-index infrared chalcogenide glass lens with the maximum refractive index span delta n of 0.48 at a wave band of 10 mu m, wherein the gradient-refractive-index infrared chalcogenide glass lens is prepared by sequentially stacking 11 basic samples with flat surfaces and different components according to the refractive index and performing precision compression molding, and the values of x in the components of the 11 basic samples are respectively 0, 6, 12, 18, 24, 30, 36, 42, 48, 54 and 60, and the preparation method comprises the following steps: melting a glass column by a melting quenching method, slicing by using an internal cutting machine, precisely grinding and polishing by using a die, and then performing press molding by using a precise molding press according to the flow of fig. 1 and pressing by using a planar die shown in fig. 2 (in fig. 2, 1 is an upper die surface, 2 is a lower die surface, 3 is 11 stacked base sample sheets, and 4 is a gradient-refractive-index infrared chalcogenide glass lens obtained by die pressing), thereby obtaining the gradient-refractive-index infrared chalcogenide glass lens of example 1, which comprises the following specific preparation steps:
(1) Determining the components of each basic sample, and respectively determining the components of the basic samples with different values of x, namely 0, 6, 12, 18, 24, 30, 36, 42, 48, 54 and 60The preparation method comprises the following steps: according to the formula As 40 S (60-x) Se x Calculating and weighing each simple substance raw material, and sequentially filling the raw materials into a quartz tube for vacuumizing so that the vacuum degree in the quartz tube is less than 10 -3 Pa, then sealing the quartz tube by using acetylene-oxygen flame; putting the sealed quartz tube into a swinging furnace, heating to 750-850 ℃ for 10-12h, swinging and melting for 8-25h, discharging, cooling by adopting a water cooling mode, then putting the quartz tube into an annealing furnace at 160-170 ℃, preserving heat for 2h, naturally cooling to room temperature, removing the wall to obtain glass columns, and then respectively slicing, grinding and polishing the glass columns into sheets with the thickness of 0.6 +/-0.02 mm;
(2) Stacking the processed 11 pieces of basic sample sheets in order according to the refractive index, placing the stacked basic sample sheets on the lower molding surface of a mold in a mold pressing cabin of a precision mold press, closing the mold pressing cabin, filling nitrogen to ensure that glass is not oxidized in the mold pressing process, then raising the lower molding surface of the mold until the upper surface of the uppermost basic sample sheet is flush with the bottom surface of the upper molding surface of the mold in the mold pressing cabin, and recording the distance between the upper molding surface of the mold and the lower molding surface of the mold as an initial distance S 0 ＝6.6mm；
(3) Heating the upper mold surface and the lower mold surface of the mold for the first time, and rapidly heating the upper mold surface and the lower mold surface of the mold to 166 ℃ at a heating rate of 70 ℃/min;
(4) Heating the upper and lower mold surfaces for the second time, slowly heating the upper mold surface to a temperature 10-50 deg.C (266 deg.C) above the softening temperature of the uppermost basic sample sheet, slowly heating the lower mold surface to a temperature 10-50 deg.C (240 deg.C) above the softening temperature of the lowermost basic sample sheet, keeping the temperature for 200S to soften 11 basic sample sheets, keeping the temperatures of the upper and lower mold surfaces constant, slowly raising the lower mold surface, gradually pressurizing the softened basic sample to a certain pressure, and pressing at a constant temperature of 0.4kN until the distance between the upper and lower mold surfaces reaches a preset target distance S 1 =4.62mm; in the step (4), the heating rate of the upper mold surface and the lower mold surface is 5-10 ℃/min;
(5) Keeping the positions of the upper mold surface and the lower mold surface unchanged, controlling the nitrogen purging speed, slowly cooling, and slowly cooling the temperatures of the upper mold surface and the lower mold surface to 140-170 ℃ at a cooling rate of 5-20 ℃/min; then accelerating the nitrogen purging speed, rapidly cooling, and stopping introducing nitrogen when the temperature of the upper mold surface and the lower mold surface of the mold is rapidly reduced to 25 ℃ at the cooling rate of 40-80 ℃/min;
(6) And opening the mold ballast to lower the lower mold surface of the mold to release the pressure, taking out the infrared chalcogenide glass sample with the gradient refractive index, and polishing the sample by using 8000 meshes of polishing solution to obtain the infrared chalcogenide glass lens with the gradient refractive index of the example 1.
The gradient-index infrared chalcogenide glass lens of example 1 is tested on a Fourier infrared spectrometer, and the result shows that the lens still maintains good transmittance in a 2.5-12.5 μm wave band, which proves that the thermal stability of a base sample is good and crystals are not precipitated to influence the transmittance. In addition, an infrared thermal imaging camera is adopted to observe the gradient-refractive-index infrared chalcogenide glass lens, and the defect such as bubbles and the like does not appear in the lens. A strip-shaped sample is taken out from the middle part of the gradient-refractive-index infrared chalcogenide glass lens, the cross section of the sample is scanned by an EDX (enhanced dispersive X) and confocal Raman spectrometers, the refractive index distribution of the obtained lens is represented by two means and is step-shaped, as shown in figure 4, and the result shows that the maximum refractive index span delta n of the lens at a 10-micron waveband can reach 0.48. As indicated on the abscissa of FIG. 4 2 Se 3 Layer refers to the base sample with x having a value of 60, sample a. In fig. 4, letters J-a from top to bottom correspond to 11 pieces of base samples in which x is 0, 6, 12, 18, 24, 30, 36, 42, 48, 54, and 60, and broken line segments of refractive index distributions at wavelength bands of 2 μm, 4 μm, and 10 μm are arranged from top to bottom.
Example 2: a curved gradient index infrared chalcogenide glass lens having a maximum refractive index span Deltan of 0.48 at a wavelength of 10 μm was prepared. The mold pressing mold used in example 2 was a curved mold, and the lens prepared was a curved gradient index infrared chalcogenide glass lens. The gradient-refractive-index infrared chalcogenide glass lens is prepared by sequentially stacking 11 basic samples with flat surfaces and different components according to the refractive index and performing precision compression molding, wherein the values of x in the components of the 11 basic samples are respectively 0, 6, 12, 18, 24, 30, 36, 42, 48, 54 and 60, and the preparation method comprises the following steps: the glass column is melted by a fusion quenching method, then the glass column is sliced by an inner circle cutting machine, the precision grinding and polishing are carried out by a mould, then the glass column is pressed and formed by a precision moulding press according to the flow of figure 1, and the curved surface mould shown in figure 3 is adopted for pressing, so that the infrared chalcogenide glass lens with the gradient refractive index of the embodiment 2 is obtained, and the preparation steps are as follows:
(1) Determining the components of each basic sample, and preparing the basic samples with different components, wherein x is 0, 6, 12, 18, 24, 30, 36, 42, 48, 54 and 60, into slices according to the following methods: according to the formula As 40 S (60-x) Se x Calculating and weighing each simple substance raw material, and sequentially filling the raw materials into a quartz tube for vacuumizing so that the vacuum degree in the quartz tube is less than 10 -3 Pa, then sealing the quartz tube by using acetylene-oxygen flame; putting the sealed quartz tube into a rocking furnace, heating to 750-850 ℃ for 10-12h, rocking and melting for 8-25h, discharging, cooling by adopting a water cooling mode, then putting the quartz tube into an annealing furnace at 160-170 ℃ for heat preservation for 2h, naturally cooling to room temperature, removing the wall to obtain glass columns, and then respectively slicing, grinding and polishing the glass columns into sheets with the thickness of 0.6 +/-0.02 mm;
(2) Sequentially stacking 11 processed basic sample sheets according to the refractive index, placing the processed basic sample sheets on a lower mold surface in a mold pressing cabin of a precise mold pressing machine, closing the mold pressing cabin, filling nitrogen to ensure that glass is not oxidized in the mold pressing process, then raising the lower mold surface until the upper surface of the topmost basic sample sheet is flush with the bottom surface of the upper mold surface in the mold pressing cabin, and marking the distance between the upper mold surface and the lower mold surface as an initial distance S 0 ＝6.6mm；
(3) Heating the upper mold surface and the lower mold surface for the first time, and rapidly heating the upper mold surface and the lower mold surface to 166 ℃ at a heating rate of 60 ℃/min;
(4) Matched mouldHeating the upper mold surface and the lower mold surface for the second time, slowly heating the upper mold surface to a temperature which is 10-50 ℃ (266 ℃) higher than the softening temperature of the uppermost layer of the basic sample sheet, slowly heating the lower mold surface to a temperature which is 10-50 ℃ (240 ℃) higher than the softening temperature of the lowermost layer of the basic sample sheet, preserving heat for 250S, softening 11 pieces of basic sample sheets, keeping the temperatures of the upper mold surface and the lower mold surface unchanged, slowly raising the lower mold surface, gradually pressurizing the softened basic sample to a certain pressure, pressing at a constant temperature of 0.5kN until the distance between the upper mold surface and the lower mold surface reaches a preset target distance S 1 =4.62mm; in the step (4), the heating rate of the upper mold surface and the lower mold surface is 5-10 ℃/min;
(5) Keeping the positions of the upper mold surface and the lower mold surface unchanged, controlling the nitrogen purging speed, slowly cooling, and slowly cooling the temperatures of the upper mold surface and the lower mold surface to 140-170 ℃ at the cooling rate of 5-20 ℃/min; then accelerating the nitrogen purging speed, rapidly cooling, and stopping introducing nitrogen when the temperature of the upper mold surface and the lower mold surface of the mold is rapidly reduced to 27 ℃ at the same time at the cooling rate of 40-80 ℃/min;
(6) And opening the mold ballast to lower the lower mold surface of the mold to release the pressure, taking out the infrared chalcogenide glass sample with the gradient refractive index, and polishing the sample by using 8000 meshes of polishing solution to obtain the infrared chalcogenide glass lens with the gradient refractive index of the example 2.
For the gradient-index infrared chalcogenide glass lens of example 2, the infrared thermal imaging camera was used to observe the gradient-index infrared chalcogenide glass lens, which showed that no bubbles or other defects appeared in the lens. A strip-shaped sample is taken out from the middle part of the gradient-refractive-index infrared chalcogenide glass lens, the cross section of the sample is subjected to line scanning by using an EDX (enhanced double-diffraction) and confocal Raman spectrometer, the refractive index distribution of the obtained lens is represented by two means to be step-shaped, and the result shows that the maximum refractive index span delta n of the lens at a wave band of 10 mu m can reach 0.48.
Example 3: the preparation method comprises the following steps of preparing a plane gradient refractive index infrared chalcogenide glass lens with the maximum refractive index span delta n of 0.3 at a wave band of 10 mu m, wherein the gradient refractive index infrared chalcogenide glass lens is prepared by sequentially stacking 7 basic samples with flat surfaces and different components according to the refractive index and performing precision compression molding, and the values of x in the components of the 7 basic samples are respectively 0, 6, 12, 18, 24, 30 and 36, and the preparation method comprises the following steps: melting a glass column by a melting quenching method, slicing by using an internal circle cutting machine, precisely grinding and polishing by using a mold, performing compression molding by using a precise molding press according to the flow of fig. 1, and pressing by using a plane mold shown in fig. 2 to obtain the gradient-refractive-index infrared chalcogenide glass lens of the embodiment 3, wherein the preparation method comprises the following specific steps:
(1) Determining the components of each basic sample, and preparing the basic samples with different components, wherein the values of x are respectively 0, 6, 12, 18, 24, 30 and 36 into slices according to the following methods: according to the formula As 40 S (60-x) Se x Calculating and weighing each simple substance raw material, and sequentially filling the raw materials into a quartz tube for vacuumizing so that the vacuum degree in the quartz tube is less than 10 -3 Pa, then sealing the quartz tube by using acetylene-oxygen flame; putting the sealed quartz tube into a swinging furnace, heating to 750-850 ℃ for 10-12h, swinging and melting for 8-25h, discharging, cooling by adopting a water cooling mode, then putting the quartz tube into an annealing furnace at 160-170 ℃, preserving heat for 2h, naturally cooling to room temperature, removing the wall to obtain glass columns, and then respectively slicing, grinding and polishing the glass columns into sheets with the thickness of 0.6 +/-0.02 mm;
(2) Stacking the processed 7 pieces of basic sample sheets in order according to the refractive index, placing the sheets on the lower surface of a mold in a mold pressing cabin of a precision mold press, closing the mold pressing cabin, filling nitrogen to ensure that glass is not oxidized in the mold pressing process, then lifting the lower surface of the mold until the upper surface of the uppermost layer of the basic sample sheet is flush with the bottom surface of the upper surface of the mold in the mold pressing cabin, and recording the distance between the upper surface of the mold and the lower surface of the mold as an initial distance S 0 ＝4.2mm；
(3) Heating the upper mold surface and the lower mold surface of the mold for the first time, and rapidly heating the upper mold surface and the lower mold surface of the mold to 175 ℃ at a heating rate of 70 ℃/min;
(4) Heating the upper mold surface and the lower mold surface of the mold for the second time, slowly raising the temperature of the upper mold surface to be 10-50 ℃ (266 ℃ specifically) above the softening temperature of the uppermost base sample sheet, slowly raising the temperature of the lower mold surface to be 10-50 ℃ (248 ℃ specifically) above the softening temperature of the lowermost base sample sheet, keeping the temperature of the upper mold surface and the lower mold surface unchanged, slowly raising the lower mold surface, gradually pressurizing the softened base sample to a certain pressure, pressing at a constant temperature of 0.8kN until the distance between the upper mold surface and the lower mold surface reaches a preset target distance S, and keeping the temperature of the lower mold surface at a constant value for 200S 1 =2.94mm; in the step (4), the heating rate of the upper mold surface and the lower mold surface is 5-10 ℃/min;
(5) Keeping the positions of the upper mold surface and the lower mold surface unchanged, controlling the nitrogen purging speed, slowly cooling, and slowly cooling the temperatures of the upper mold surface and the lower mold surface to 140-170 ℃ at a cooling rate of 5-20 ℃/min; then accelerating the nitrogen purging speed, rapidly cooling, and stopping introducing nitrogen when the temperature of the upper mold surface and the lower mold surface of the mold is rapidly reduced to 23 ℃ at the cooling rate of 40-80 ℃/min;
(6) And opening the mold pressing cabin to lower the lower mold surface of the mold to release the pressure, taking out the infrared chalcogenide glass sample with the gradient refractive index, and polishing the sample by using a polishing solution with 8000 meshes to obtain the infrared chalcogenide glass lens with the gradient refractive index of the example 3.
The gradient-index infrared chalcogenide glass lens in example 3 is tested on a Fourier infrared spectrometer, and the result shows that the good transmittance is still maintained in the 2.5-12.5 μm waveband, which proves that the thermal stability of a base sample is good and crystals are not precipitated to influence the transmittance. In addition, an infrared thermal imaging camera is adopted to observe the gradient-refractive-index infrared chalcogenide glass lens, and the defect such as bubbles and the like does not appear in the lens. A strip-shaped sample is taken out from the middle part of the gradient-refractive-index infrared chalcogenide glass lens, the cross section of the sample is subjected to line scanning by using an EDX (enhanced double-diffraction) and confocal Raman spectrometer, the refractive index distribution of the obtained lens is represented by two means to be step-shaped, and the result shows that the maximum refractive index span delta n of the lens at a wave band of 10 mu m can reach 0.3.
Example 4: the preparation method comprises the following steps of preparing a plane gradient refractive index infrared chalcogenide glass lens with the maximum refractive index span delta n of 0.23 at a wave band of 10 mu m, wherein the gradient refractive index infrared chalcogenide glass lens is prepared by sequentially stacking 5 basic samples with flat surfaces and different components according to the refractive index and performing precision compression molding, and the values of x in the components of the 5 basic samples are respectively 0, 6, 12, 18 and 24, and the preparation method comprises the following steps: melting a glass column by a melting quenching method, slicing by using an internal circle cutting machine, precisely grinding and polishing by using a mold, performing compression molding by using a precise molding press according to the flow of fig. 1, and pressing by using a plane mold shown in fig. 2 to obtain the gradient-refractive-index infrared chalcogenide glass lens of example 4, wherein the preparation steps are as follows:
(1) Determining the components of each basic sample, and preparing the basic samples with different components, wherein the values of x are respectively 0, 6, 12, 18 and 24 into slices according to the following methods: according to the formula As 40 S (60-x) Se x Calculating and weighing each simple substance raw material, and sequentially filling the raw materials into a quartz tube for vacuumizing so that the vacuum degree in the quartz tube is less than 10 -3 Pa, then sealing the quartz tube by using acetylene-oxygen flame; putting the sealed quartz tube into a swinging furnace, heating to 750-850 ℃ for 10-12h, swinging and melting for 8-25h, discharging, cooling by adopting a water cooling mode, then putting the quartz tube into an annealing furnace at 160-170 ℃, preserving heat for 2h, naturally cooling to room temperature, removing the wall to obtain glass columns, and then respectively slicing, grinding and polishing the glass columns into sheets with the thickness of 0.6 +/-0.02 mm;
(2) Stacking the processed 5 pieces of basic sample sheets in order according to the refractive index, placing the stacked basic sample sheets on the lower molding surface of a mold in a mold pressing cabin of a precision mold press, closing the mold pressing cabin, filling nitrogen to ensure that glass is not oxidized in the mold pressing process, then raising the lower molding surface of the mold until the upper surface of the uppermost basic sample sheet is flush with the bottom surface of the upper molding surface of the mold in the mold pressing cabin, and recording the distance between the upper molding surface of the mold and the lower molding surface of the mold as an initial distance S 0 ＝3mm；
(3) Heating the upper mold surface and the lower mold surface of the mold for the first time, and rapidly heating the upper mold surface and the lower mold surface of the mold to 182 ℃ at a heating rate of 70 ℃/min;
(4) Heating the upper mold surface and the lower mold surface of the mold for the second time, slowly raising the temperature of the upper mold surface to be 10-50 ℃ (266 ℃ specifically) above the softening temperature of the uppermost base sample sheet, slowly raising the temperature of the lower mold surface to be 10-50 ℃ (245 ℃ specifically) above the softening temperature of the lowermost base sample sheet, keeping the temperature of the upper mold surface and the lower mold surface unchanged, slowly raising the lower mold surface, gradually pressurizing the softened base sample to a certain pressure, pressing at a constant temperature of 0.2kN until the distance between the upper mold surface and the lower mold surface reaches a preset target distance S, and keeping the temperature of the upper mold surface and the lower mold surface constant 1 =2.1mm; in the step (4), the heating rate of the upper mold surface and the lower mold surface is 5-10 ℃/min;
(5) Keeping the positions of the upper mold surface and the lower mold surface unchanged, controlling the nitrogen purging speed, slowly cooling, and slowly cooling the temperatures of the upper mold surface and the lower mold surface to 140-170 ℃ at a cooling rate of 5-20 ℃/min; then accelerating the nitrogen purging speed, rapidly cooling, and stopping introducing nitrogen when the temperature of the upper mold surface and the lower mold surface of the mold is rapidly reduced to 24 ℃ at the same time at the cooling rate of 40-80 ℃/min;
(6) And opening the mold pressing cabin to lower the lower mold surface of the mold to release the pressure, taking out the infrared chalcogenide glass sample with the gradient refractive index, and polishing the sample by using polishing liquid with 8000 meshes to obtain the infrared chalcogenide glass lens with the gradient refractive index of the example 4.
The gradient-index infrared chalcogenide glass lens of example 4 is tested on a Fourier infrared spectrometer, and the result shows that the good transmittance is still maintained in the 2.5-12.5 μm wave band, which proves that the thermal stability of the basic sample is good and the transmittance is not influenced by the precipitated crystal. In addition, an infrared thermal imaging camera is adopted to observe the gradient-refractive-index infrared chalcogenide glass lens, and the defect such as bubbles and the like does not appear in the lens. A strip sample is taken out from the middle part of the gradient-refractive-index infrared chalcogenide glass lens, the cross section of the sample is scanned by an EDX (enhanced dispersive X) and confocal Raman spectrometers, the refractive index distribution of the obtained lens is represented by two means to be step-shaped, and the result shows that the maximum refractive index span delta n of the lens at a 10 mu m wave band can reach 0.23.
Claims (7)
1. The gradient-refractive-index infrared chalcogenide glass lens is characterized by being prepared by sequentially stacking a plurality of base samples with flat surfaces and different components according to refractive index and performing precision compression molding, wherein the molar composition of each base sample is expressed As As according to a chemical formula 40 S (60-x) Se x Wherein x is more than or equal to 0 and less than or equal to 60.
2. The gradient index infrared chalcogenide glass lens of claim 1 wherein the chemical formula is As 40 S (60-x) Se x The difference between the maximum glass transition temperature and the minimum glass transition temperature of the glass composition of (1) is less than or equal to 30 ℃.
3. A method for preparing a gradient index infrared chalcogenide glass lens according to claim 1 or 2, comprising the steps of:
(1) The composition of each base sample was determined and for the different components of the base sample, flakes were prepared according to the following method, respectively: according to the formula As 40 S (60-x) Se x Calculating and weighing each simple substance raw material, and sequentially filling the raw materials into a quartz tube for vacuumizing to ensure that the vacuum degree in the quartz tube is less than 10 -3 Pa, then sealing the quartz tube by using acetylene-oxygen flame; putting the sealed quartz tube into a swinging furnace, heating to 750-850 ℃ for 10-12h, swinging and melting for 8-25h, discharging, cooling by adopting a water cooling mode, then putting the quartz tube into an annealing furnace at 160-170 ℃, preserving heat for 2h, naturally cooling to room temperature, removing the wall to obtain glass columns, and then respectively slicing, grinding and polishing the glass columns into slices;
(2) Sequentially stacking a plurality of processed basic sample sheets according to the refractive index, placing the processed basic sample sheets on a lower mold surface in a mold pressing cabin of a precise mold pressing machine, closing the mold pressing cabin, filling nitrogen, and then lifting the lower mold surface of the mold until the upper surface of the uppermost basic sample sheet is flush with the bottom surface of the upper mold surface in the mold pressing cabin;
(3) Heating the upper mold surface and the lower mold surface for the first time, and rapidly heating the upper mold surface and the lower mold surface to 160-185 ℃ respectively;
(4) Heating the upper mold surface and the lower mold surface of the mold for the second time, slowly raising the temperature of the upper mold surface of the mold to be 10-50 ℃ higher than the softening temperature of the uppermost base sample sheet, slowly raising the temperature of the lower mold surface of the mold to be 10-50 ℃ higher than the softening temperature of the lowermost base sample sheet, preserving the heat for 200-400 seconds to soften the base sample sheets, keeping the temperatures of the upper mold surface and the lower mold surface unchanged, slowly raising the lower mold surface of the mold, gradually pressurizing the softened base sample to a certain pressure, and pressing at constant temperature until the distance between the upper mold surface and the lower mold surface of the mold reaches a preset target distance;
(5) Keeping the positions of the upper mold surface and the lower mold surface unchanged, controlling the nitrogen purging speed, slowly cooling, and slowly cooling the temperatures of the upper mold surface and the lower mold surface to 140-170 ℃ respectively; then, the nitrogen purging speed is increased, the temperature is rapidly reduced, and when the upper die surface and the lower die surface are simultaneously and rapidly reduced to the room temperature, the introduction of nitrogen is stopped;
(6) And opening the mold ballast to enable the lower mold surface of the mold to descend so as to release the pressure, taking out the infrared chalcogenide glass sample with the gradient refractive index and polishing the infrared chalcogenide glass sample to obtain the infrared chalcogenide glass lens with the gradient refractive index.
4. The method for preparing gradient index infrared chalcogenide glass lenses according to claim 3, wherein the temperature rise rate of the upper mold surface and the lower mold surface in the step (3) is 50-100 ℃/min; in the step (4), the heating rate of the upper mold surface and the lower mold surface is 5-10 ℃/min; the cooling rate of slow cooling in the step (5) is 5-20 ℃/min, and the cooling rate of rapid cooling is 40-80 ℃/min.
5. The method for producing a gradient-index infrared chalcogenide glass lens according to claim 3, wherein when an upper surface of an uppermost base sample sheet in the step (2) is flush with a bottom surface of an upper mold surface in a mold pressing chamber, a distance between the upper mold surface and a lower mold surface is regarded as an initial distance S 0 (ii) a After the pressurization in the step (4) is finished, the distance between the upper mold surface and the lower mold surface is recorded as S 1 Then S is 1 ＝40-80％S 0 。
6. The method for producing a gradient-index infrared chalcogenide glass lens according to claim 3, wherein the pressure at the constant temperature pressing in the step (4) is 0.2 to 0.8kN.
7. The method of claim 3, wherein the upper and lower mold surfaces are flat or curved.
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