GRIN Lens Manufacturing via Controlled Sintering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for manufacturing graded index (GRIN) lenses with high numerical aperture (NA) and small diameter are hindered by foaming issues during high-temperature stretching, leading to instability and poor reliability, especially in the sol-gel process.
Innovation Solution
A method involving the formation of a wet gel with a refractive index distribution using metal alkoxides, followed by sintering at controlled oxygen partial pressures (≤10−1 Pa) and temperature increase rates (v ≦ 105*EXP(-12ρ)) to prevent foaming, allowing for the production of GRIN lenses with NA ≥ 0.4 and diameters of 1 mm or smaller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the sol-gel process is used to manufacture GRIN lenses with high NA and small diameter, then the manufacturing precision and optical performance are improved, but foaming occurs during high-temperature stretching leading to poor reliability
Solution Approach 1:
The patent applies parameter changes by precisely controlling the sintering temperature profile and oxygen partial pressure during the sol-gel process. Specifically, the sintering is performed in two stages: first at 800-1000°C to remove organic components, then at 1100-1500°C to form the glass matrix, with oxygen partial pressure controlled at 10-100 Pa. This controlled parameter approach prevents foaming while achieving the desired high NA and small diameter specifications.
Solution Approach 2:
The patent employs an inert atmosphere (vacuum or inert gas environment) during the sintering process to control oxygen partial pressure at 10-100 Pa. This inert environment prevents oxidation reactions that would generate gas bubbles and cause foaming, while still allowing the formation of the desired glass matrix structure with the required refractive index distribution.
2Manufacturing precision
If high loads of additives (GeO2, P2O5) are increased to obtain NA of 0.38 or more, then the light-condensing performance is improved, but the coefficient of thermal expansion becomes large causing cracking and air bubbles
Solution Approach 1:
The patent changes the compositional parameters by using metal alkoxides (such as germanium alkoxide, phosphorus alkoxide, or titanium alkoxide) as precursors instead of direct metal oxide additives. This allows precise control of the refractive index distribution through the sol-gel process while maintaining thermal stability. The metal alkoxides form a gel structure that prevents excessive thermal expansion and cracking during subsequent heating processes.
Solution Approach 2:
The patent creates a composite gel structure by combining metal alkoxides with silica sol in controlled ratios. This composite approach allows the formation of a homogeneous matrix with distributed metal oxide nanoparticles, achieving high NA through controlled refractive index variation while the gel structure provides thermal stability and prevents cracking during processing.
3Volume of moving object
If the GRIN lens base material is stretched at high temperature (1800-2000°C) to reduce diameter to 1 mm or smaller, then the miniaturization is achieved, but foaming occurs making the process unstable
Solution Approach 1:
The patent performs preliminary actions by completing the sintering and densification process before the stretching operation. The base material is pre-sintered at 1100-1500°C in a controlled oxygen atmosphere to remove all organic components and establish a stable glass matrix structure. This preliminary treatment eliminates the source of foaming (organic residues) before stretching, ensuring stable miniaturization to 1 mm diameter or smaller without foaming during the stretching process.
Solution Approach 2:
The patent changes the temperature parameter profile by using a two-stage heating process: first sintering at 800-1000°C to remove organics, then at 1100-1500°C to form the glass matrix, followed by controlled stretching at lower temperatures (below the softening point). This parameter optimization prevents foaming during stretching while achieving the required small diameter.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the stable manufacturing of GRIN lenses with high NA and small diameters, preventing foaming and ensuring the lenses can be miniaturized and efficiently used in optical devices without cracking or shrinkage, facilitating self-alignment with optical fibers.
Implementation Method 1
sintering the dry gel to form a GRIN lens base material
Implementation Method 2
the gel is sintered to thereby make dense glass
Implementation Method 3
an alcoholic solution including an alkoxide of silicon as a main component is added to acids or bases as solvents and hydrolysis is performed to make sol
Implementation Method 4
this sol is further subjected to a polycondensation reaction, thus a crosslinking reaction proceeds to make a wet gel
Implementation Method 5
the obtained wet gel is dried, the solvent in the gel is removed
Data Source
AI summary
A method for manufacturing a GRIN lens includes the steps of forming a wet gel provided with a concentration distribution having a different concentration of a refractive index distribution imparting metal that differs in concentration in a radial direction, drying the wet gel to form a dry gel having a bulk specific gravity ρ (g/cm3), sintering the dry gel to form a GRIN lens base material and stretching the GRIN lens base material while heating. The method is characterized in that, in the step of sintering the dry gel, partial pressures of oxygen during sintering at 800° C. or higher are 10−1 Pa or lower and also the relation between a rate of temperature increase v (° C./hr) and a bulk density ρ of the dry gel during sintering at 1,000 to 1,150° C. is defined by v≦105*EXP (−12ρ). As a result of this, the GRIN lens, which has a large numerical aperture and a small diameter, can stably and easily be manufactured.