Tunable Lens Chromatic Aberration Compensation
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Solution Overview
Problem
Optical imaging systems face challenges in maintaining consistent focus across different spectral bands due to chromatic aberration, where lenses focus light from various wavelengths at different distances, leading to blurred and distorted images, especially in hyperspectral imaging that spans ultraviolet, visible, and infrared ranges.
Innovation Solution
An electrically tunable lens system that adjusts focus based on stored adjustment data for each spectral band, ensuring accurate focus by compensating for the differences in focal lengths across the electromagnetic spectrum, allowing for rapid and efficient capture of high-quality hyperspectral images without the need for continuous focus verification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a traditional fixed focal length lens is used for hyperspectral imaging, then the device complexity is low, but the focus consistency across different spectral bands deteriorates due to chromatic aberration
Solution Approach 1:
The patent applies a tunable lens that can dynamically adjust its focal length based on the spectral band being imaged. The lens focal length is electrically tuned to compensate for chromatic aberration, allowing the system to maintain focus consistency across different wavelengths without requiring multiple fixed lenses or complex mechanical adjustments.
Solution Approach 2:
The system changes the optical parameters of the lens by adjusting its focal length according to the specific spectral band being captured. The control system modifies the lens focal length parameter in response to different illumination wavelengths, transforming a static optical system into an adaptive one that compensates for wavelength-dependent focus shifts.
2Manufacturing precision
If manual focus adjustment is performed for each spectral band, then the focus accuracy is improved, but the imaging speed deteriorates due to time-consuming focus verification
Solution Approach 1:
The system performs preliminary focus adjustment by pre-determining the optimal lens focal length for each spectral band. The control system calculates or stores the required focal length adjustments in advance, so when imaging a specific spectral band, the lens is already positioned at the correct focus without requiring real-time verification or iterative adjustment during capture.
Solution Approach 2:
The control system automatically determines and adjusts the lens focal length based on the detected spectral band without requiring manual intervention. The system self-regulates the focus by monitoring the illumination wavelength and autonomously tuning the lens parameter, eliminating the need for operator involvement in focus verification for each band.
3Adaptability or versatility
If the lens focal length is adjusted in real-time during imaging, then the focus adaptability is improved, but the system latency increases due to continuous adjustment operations
Solution Approach 1:
The system adjusts the lens focal length periodically based on changes in spectral band rather than continuously. The control system monitors the illumination wavelength and only triggers lens adjustment when the spectral band changes, maintaining a stable focal length during each band's capture. This periodic adjustment approach reduces unnecessary operations and minimizes latency while preserving adaptability across different bands.
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 system enables precise and consistent focus across multiple spectral bands, reducing latency and improving image quality by pre-adjusting the lens position based on wavelength, enabling earlier detection of defects in objects like fruit through hyperspectral imaging.
Implementation Method 1
Many lens and lens assemblies exhibit chromatic aberration, where the effective focal distance or focal length of a lens assembly is slightly different for different wavelengths. The refractive index of lens elements typically varies with the wavelength of light, resulting in changes in focal length for different wavelength.
Implementation Method 2
The refractive index of lens elements typically varies with the wavelength of light, resulting in changes in focal length for different wavelength.
Data Source
AI summary
A system and method for automated lens adjustment for hyperspectral imaging is described. The system includes an image sensor and an electrically-controllable element arranged to set a spectral band for image capture by (i) selectively providing light for a selected spectral band or (ii) selectively filtering light to a selected spectral band. The system includes a tunable lens that is adjustable to change a focal length of the lens; and one or more data storage devices storing data that indicates different focus adjustment parameters corresponding to different spectral bands. The system includes a control system configured to perform operations including: selecting a spectral band; controlling the electrically-controllable element to set the spectral band for image capture; retrieving the focus adjustment parameter that corresponds to the spectral band; adjusting the lens based on the retrieved focus adjustment parameter; and capturing an image of the subject while the lens remains adjusted.