Diffractive Optical Element Sintering Precision
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Solution Overview
Problem
Existing machining methods for diffractive optical elements, particularly those using cutting tools with hard materials like ceramic, suffer from tool abrasion issues, leading to reduced precision and increased manufacturing costs, while sintering and compression molding do not adequately enhance optical characteristics.
Innovation Solution
A diffractive optical element with surface roughness of 0.05 μm or less and a sintered ceramic body where prominent and groove portions have radii of curvature larger than half the average grain size, along with a die configuration that facilitates precise molding and reduces tool wear, enhancing machining precision and optical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a cutting tool is used to machine a ceramic diffractive optical element, then the optical characteristics can be improved through precise machining, but the cutting tool becomes progressively abraded, reducing production efficiency and increasing manufacturing cost
Solution Approach 1:
The patent replaces the mechanical cutting system with a sintering and compression molding system. Instead of using cutting tools to remove material, the diffractive optical element is formed by sintering ceramic powder in a mold that directly creates the desired surface structure with prominent portions and groove portions. This eliminates tool abrasion while achieving the required surface roughness of Ra ≤ 0.05 μm
Solution Approach 2:
The patent changes the material state from solid ceramic requiring mechanical cutting to ceramic powder that can be sintered and molded. By controlling the sintering temperature, pressure, and mold design (with radius of curvature ≥ half the grain size), the process achieves precise surface geometry without mechanical tool wear
2Reliability
If a diamond tool is used as the cutting tool, then the progress of abrasion is suppressed to a certain degree, but the manufacturing cost increases and the improvement to machining precision is not necessarily adequate
Solution Approach 1:
The patent eliminates the need for diamond cutting tools by replacing the mechanical cutting process with sintering and compression molding. The mold itself, made from durable material, directly forms the diffractive structure through heat and pressure, achieving Ra ≤ 0.05 μm surface finish without any tool abrasion issues
Solution Approach 2:
The process transitions from mechanical removal (cutting) to thermal-forming (sintering). By controlling sintering temperature and pressure parameters, the ceramic powder is consolidated into the final shape with precise surface geometry, eliminating the need for expensive diamond tools while maintaining or improving precision
3Productivity
If sintering and compression molding are used to manufacture a ceramic diffractive optical element, then the problem of cutting tool abrasion is significantly reduced, but adequate machining precision is not necessarily obtained and optical characteristics are not adequately enhanced
Solution Approach 1:
The patent applies local quality control by designing the mold with specific geometric parameters (radius of curvature at least half the grain size) that directly transfer to the diffractive element surface. The mold's surface characteristics in the optical effective area are optimized to produce Ra ≤ 0.05 μm, while other areas of the element can have different properties
Solution Approach 2:
The precise surface geometry is created during the sintering and compression molding process itself, before any subsequent machining. The mold pre-forms the prominent portions and groove portions with the required precision, eliminating the need for post-sintering machining and ensuring the surface roughness requirement is met from the start
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
The method achieves enhanced optical characteristics and reduced manufacturing costs by improving machining precision and extending die durability, while maintaining low production costs.
Implementation Method 1
Diffractive optical elements (DOE) for focusing light and performing other functions by utilizing a light diffraction phenomenon to change the direction in which light is propagated
Data Source
AI summary
A diffractive optical element (1) composed of a ceramic, in which the optical characteristics are enhanced by enhancing the machining precision, is composed of an infrared-transmissive ceramic, and prominent portions (11) and groove portions (12) are repeatedly formed on a surface of the diffractive optical element (1). The average value of the surface roughness Ra within an optical effective area (10) of the surface of the diffractive optical element is 0.05 μm or less, and the difference in the surface roughness Ra within the optical effective area (10) of the surface is 0.02 μm or less.