Aspheric Apochromatic Optical System with Calcium Fluorite
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High resolution optical imaging systems require lens assemblies that reduce the number of lens elements while maintaining image quality and manufacturing efficiency, and existing two-element lens assemblies often have lower focal ratios or Strehl Numbers, complicating and costing more to manufacture.
Innovation Solution
A two-element optical lens assembly with aspheric surfaces, comprising a negative and positive optical power lens element, configured to achieve a Strehl Number of 80% or more within the 0.435-0.706 μm spectral range and a focal ratio between F/5-F/12, using calcium fluorite crystal and glass materials with specific refractive indices and dispersion properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If spherical-surface glass lenses are used in prior art lens assemblies, then chromatic aberration can be corrected by adhering two spherical glass lenses together to form a doublet, but the number of lens elements increases and manufacturing becomes complicated and expensive
Solution Approach 1:
The patent replaces spherical lens surfaces with aspheric surfaces in the two-element lens assembly. The aspheric surfaces enable high-level chromatic aberration correction and improved image quality (Strehl Number ≥80%) while maintaining only two lens elements, avoiding the need for multiple spherical elements that would increase complexity and manufacturing cost.
2Reliability
If two spherical glass lenses are adhered together to form a doublet, then chromatic aberration is corrected, but manufacturing requirements become complicated and relatively expensive
Solution Approach 1:
The use of aspheric surfaces in just two lens elements achieves superior chromatic aberration correction compared to traditional spherical doublets. This reduces the number of elements needed and simplifies manufacturing, as fewer precision spherical surfaces need to be ground and polished, and fewer adhesives are required.
3Device complexity
If prior art two-element lens assemblies are designed, then the number of lens elements is reduced, but the focal ratio is lower (e.g. F/15) or the Strehl Number is lower
Solution Approach 1:
The patent employs aspheric surfaces on the lens elements to correct spherical aberration and improve focus, achieving a Strehl Number of 80% or more. This allows the two-element assembly to maintain high image quality across a wider range of focal ratios (F/5-F/12) compared to traditional spherical two-element designs.
4Manufacturing precision
If more lens elements are used in high resolution optical imaging systems, then image quality is maintained, but the number of lens elements increases and manufacturing efficiency decreases
Solution Approach 1:
The aspheric surfaces in the two-element lens assembly provide superior correction of spherical aberration and improved focus compared to multiple spherical elements. This achieves high-resolution imaging with fewer elements, reducing manufacturing steps, alignment requirements, and assembly complexity, thereby improving manufacturing efficiency.
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 solution provides high-level chromatic aberration correction and maintains image quality with reduced lens elements, achieving performance comparable to more complex lens assemblies, while simplifying manufacturing and reducing costs.
Implementation Method 1
an optical imaging lens assembly over 95 mm clear aperture having focal ratio within F/5-F/12 range comprising two lens elements
Data Source
AI summary
The invention provides an optical imaging lens assembly comprising two lens elements (a positive optical power lens element and a negative optical power lens element) separated by an air gap. The positive lens element of the system may comprise fluorite crystal (CaF2) or other material with similar optical properties. The negative lens element of the system may be made from an optical material, typically glass, having a refractive index ne that lies within the 1.56<ne<1.70 range, and having a main dispersion (nF−nC) within the 0.00860<(nF−nC)<0.01240 range. The lens assembly may include at least one aspherical surface. It has been found that a lens assembly in accordance with the present invention, having aspherical surface(s), achieves significant improvements in the Strehl number (equal to or higher than 80%) for the optical systems with focal ratio of between F/12 and F/5 at every wavelength in the 0.435 μm to 0.706 μm range.