Asymmetric Diffractive Grating for Spectacle Lens Color Fringe Correction
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Solution Overview
Problem
Existing methods for correcting color fringes in optical elements, such as spectacle lenses, are inadequate for non-rotationally symmetrical lenses, particularly progressive and atoric lenses, as rotationally symmetrical diffractive gratings fail to provide satisfactory results.
Innovation Solution
A method for determining a diffractive grating that follows the lines of constant thickness of non-rotationally symmetrical optical elements, allowing for effective color fringe compensation by calculating the grating lines to align with the lens's thickness isolines, thereby compensating for the refractive and prismatic effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If rotationally symmetrical diffractive gratings are used for color fringe correction, then the correction method is simple and well-established, but the correction effectiveness is insufficient for non-rotationally symmetrical optical elements
Solution Approach 1:
The patent applies asymmetry by designing diffractive gratings with non-rotationally symmetrical patterns that match the specific geometry of progressive and atoric lenses. The grating lines are configured to follow the actual contour and thickness distribution of the lens surface, rather than using standard rotationally symmetrical patterns. This asymmetric design enables effective color fringe correction for lenses with complex, non-symmetrical optical surfaces.
2Length of stationary object
If higher refractive index materials are used to reduce lens thickness, then the lens thickness is reduced, but color fringe becomes more pronounced
Solution Approach 1:
The patent converts the harmful prismatic effect that causes color fringe into a beneficial correction mechanism. By designing diffractive gratings with specific line configurations that follow the lens thickness contours, the grating introduces a controlled diffractive prismatic effect that counteracts the harmful refractive prismatic effect. This transforms the wavelength-dependent prismatic deviation from a defect into a correctable parameter, enabling color fringe elimination even in high-index thin 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
This approach enables almost complete correction of color fringes in non-rotationally symmetrical lenses, reducing fringes below a specified perception threshold and potentially reducing lens thickness, while being efficient and cost-effective.
Implementation Method 1
it is possible to achieve color fringe correction by means of a diffractive grating
Data Source
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Figure 4A~4C
AI summary
The invention relates to a computer-implemented method for determining a diffraction grating for colour fringe compensation of a refractive optical element, which method comprises recording data of the refractive optical element, and calculating the diffraction grating on the basis of the recorded data of the refractive optical element, in such a way that the grating lines of the diffraction grating follow the lines of constant thickness of the refractive optical element or the lines of the constant amount of the prism of the refractive optical element or are perpendicular to the local base setting of the prism of the refractive optical element. The invention further relates to corresponding methods and devices for producing an optical element with at least one diffraction grating that has been determined by this method.