Thin Film Diffractive Waveplate Lenses for Achromatic Imaging
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Solution Overview
Problem
Existing optical lenses face challenges with increasing weight and decreasing quality as size increases, and diffractive lenses suffer from structural discontinuities and efficiency compromises, limiting their application in large-area and broadband uses.
Innovation Solution
The development of thin film, structurally continuous diffractive waveplate lenses with optically anisotropic films that impose phase shifts on polarized beams, allowing for broadband operation and variable focal length without thickness changes, using liquid crystalline materials and photoalignment techniques to create aspherical and polarizing components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If traditional glass lenses are made larger to increase area, then the area of the lens increases, but the weight increases strongly and quality decreases
Solution Approach 1:
The patent applies this principle by replacing traditional thick glass lenses with thin film diffractive waveplate lenses. The waveplate lens is fabricated as a thin coating on a substrate, reducing weight while maintaining large area. The thin film structure achieves optical functionality through diffractive phase modulation rather than relying on bulk material thickness, enabling large aperture lenses that are lightweight and structurally continuous.
2Weight of stationary object
If diffractive Fresnel lenses are used to reduce weight and thickness, then weight and thickness decrease, but structural discontinuity adds aberrations
Solution Approach 1:
The patent applies this principle by creating a continuous phase profile that replicates the optical functionality of traditional lenses without the structural discontinuities. The diffractive waveplate lens uses a continuous rotation of optical axis orientation across the aperture, producing a continuous phase modulation that eliminates the zone plate discontinuities inherent in Fresnel lenses, thereby reducing aberrations while maintaining lightweight thin-film construction.
3Adaptability or versatility
If holographic lenses are used to achieve certain optical functions, then specific optical effects are achieved, but efficiency and dispersion are compromised
Solution Approach 1:
The patent applies this principle by using a half-wave plate configuration with controlled optical axis orientation. By adjusting the spatial variation of the optical axis angle, the lens achieves wavelength-independent phase modulation. The half-wave plate nature ensures that circularly polarized light undergoes a phase shift of ±2α regardless of wavelength, providing broadband operation with high diffraction efficiency and eliminating the dispersion compromises associated with holographic lenses.
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
Enables the fabrication of lightweight, high-quality, broadband, and variable thin film lenses and microlenses with controlled polarization, addressing the limitations of traditional lenses by providing achromatic and electrically controllable optical components.
Implementation Method 1
The thickness L of the film is defined by half-wave phase retardation condition L=λ/n∥−n⊥), where n∥ and n⊥ are the principal values of the refractive indices of the material
Implementation Method 2
Such a structure imposes a phase shift Φ=±2 α(x,y) on circular polarized beams propagating through it with the sign depending on the handedness of polarization
Implementation Method 3
The required half-wave phase retardation condition can be met for as low as a few micrometer thick films, particularly, for liquid crystalline materials
Implementation Method 4
using liquid crystalline materials and photoalignment techniques to create aspherical and polarizing components
Data Source
AI summary
The invention provides for lenses fabricated as planar thin film coatings with continuous structure. The lensing action is due to optical axis orientation modulation in the plane of the lens. The lenses of the current invention are fabricated using photoalignment of a liquid crystal polymer wherein the polarization pattern of radiation used for photoalignment is obtained by propagating the light through an optical system comprising a shape-variant nonlinear spatial light polarization modulators.