Wavelength-Dependent Aperture Filter for Optical Imaging Aberrations
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Solution Overview
Problem
Optical imaging systems face challenges in maintaining image quality across different wavelengths due to geometric aberrations and varying light intensities, leading to issues like coma, spherical aberration, and reduced contrast, especially off-axis, where one wavelength can significantly deteriorate image quality.
Innovation Solution
The implementation of a wavelength-dependent aperture filter system with central, transition, and peripheral regions, allowing differential light transmission and blocking to equalize point spread functions across multiple wavelengths, and using variable geometry vignetting to control aberrations and diffraction patterns, particularly at the system aperture or its conjugate planes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If vignetting is used to control off-axis aberrations, then image quality for high-intensity wavelengths is improved, but light transmission for low-intensity wavelengths is reduced too much
Solution Approach 1:
The patent applies different transmission characteristics to different regions of the aperture for different wavelengths. The wavelength-dependent aperture filter has a first region that transmits first wavelengths and a second region that transmits second wavelengths, allowing each wavelength range to have optimized transmission properties in specific aperture zones. This resolves the contradiction by enabling selective aberration control for high-intensity wavelengths while preserving light transmission for low-intensity wavelengths.
Solution Approach 2:
The patent changes the transmission parameter of the aperture filter based on wavelength. By using a wavelength-dependent aperture filter with regions having different transmission characteristics for different wavelength ranges, the system can adjust effective aperture size and shape differently for each wavelength, thereby controlling aberrations for bright wavelengths without excessively reducing light transmission for faint wavelengths.
2Manufacturing precision
If aperture is reduced to improve aberration-limited performance, then image quality is improved, but light throughput is reduced
Solution Approach 1:
The wavelength-dependent aperture filter divides the aperture into regions with different transmission properties for different wavelengths. This allows the system to effectively reduce aperture size for wavelengths causing aberration problems while maintaining full aperture transmission for wavelengths that need maximum light throughput, thereby resolving the contradiction between image quality improvement and light throughput preservation.
3Measurement precision
If vignetting is applied to reduce off-axis aberrations, then point spread function is improved, but contrast for low-intensity wavelengths deteriorates
Solution Approach 1:
The patent implements vignetting selectively for different wavelength ranges by using a wavelength-dependent aperture filter with regions having different transmission characteristics. The first region transmits first wavelengths while the second region transmits second wavelengths, allowing off-axis aberration control for high-intensity wavelengths without reducing contrast for low-intensity wavelengths. This resolves the contradiction by applying local quality differentiation across the aperture.
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 enhances image acuity for high-intensity wavelengths while preserving low-intensity wavelengths, improving overall image quality by adjusting diffraction and aberration performance across the field, especially off-axis, and maintaining high throughput for weaker signals.
Implementation Method 1
a first wavelength dependent filter adjacent a first conjugate of a system aperture, and a second wavelength dependent filter at a second conjugate of the system aperture, wherein the first and second wavelength dependent filters substantially equalize point spread functions of the more than one wavelength ranges
Implementation Method 2
Both the PSF and the MTF will exhibit wavelength dependencies, system aperture geometry dependencies, and aberration dependencies; i.e., MTF will be different for different wavelengths and different for different aperture geometries and will depend also on the extent to which the final wavefront is diffraction limited or aberration-limited
Data Source
Figure 1
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Figure 3A~3F
AI summary
A filter is provided, the filter including a central filter region, the central filter region to transmit a first wavelength range, a peripheral filter region, the peripheral filter region to block a second wavelength range, and a transition filter region between the central and peripheral filter regions, the transition filter region to transmit or block the second wavelength range differently than the second wavelength range is to be transmitted or blocked in the central and peripheral filter regions. More generally, there may be "N" regions and up to N-1 transition regions.