Spatially-registered Wavelength Coding via Coded Aperture
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Solution Overview
Problem
Traditional spectral imaging systems face challenges with low photon collection efficiency and the 'missing cone' problem, leading to poor signal-to-noise ratios and incomplete data cubes, especially when dealing with weak, incoherent sources.
Innovation Solution
The use of a pair of matched dispersive elements and a coded aperture to produce a spatio-spectral response in a single time step, allowing for spatially-registered wavelength coding and compressive spectral imaging, which enhances light collection efficiency and avoids the missing cone issue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a slit-based dispersive spectrometer is used, then spectral information can be obtained, but photon collection efficiency is extremely poor
Solution Approach 1:
The patent removes the slit aperture from the dispersive spectrometer design, extracting the harmful element that caused poor photon collection efficiency. By eliminating the slit, the system achieves significantly improved photon collection efficiency while maintaining spectral measurement capability through alternative coding methods.
Solution Approach 2:
The patent uses a coded aperture mask that encodes spectral information through a pattern of transmission elements. This coding approach replaces the traditional slit and allows for efficient photon collection while maintaining spectral discrimination through computational processing of the coded images.
2Measurement precision
If a rotating dispersive element is used, then light gathering efficiency is maximized, but the range of angles is limited causing missing cone problem
Solution Approach 1:
The patent divides the spectral imaging task into multiple coded aperture measurements at different orientations. Each measurement captures a specific subset of spectral information, and combining these segmented measurements through computational processing reconstructs the complete data cube without missing cone problems.
Solution Approach 2:
The patent introduces a coding dimension to the traditional rotating dispersive element approach. By encoding spectral information through the coded aperture pattern rather than relying solely on rotation angles, the system expands the sampling space and eliminates the missing cone problem while maintaining high light gathering efficiency.
3Measurement precision
If traditional spectroscopic techniques are applied, then spectral imaging can be performed, but the number of measurements required equals the number of elements in the data cube
Solution Approach 1:
The coded aperture mask serves multiple functions simultaneously: it acts as a spatial filter, a spectral encoder, and a compression device. This multi-functionality allows the system to reduce the number of measurements required while maintaining spectral imaging accuracy, as a single coded measurement encodes multiple spectral components.
Solution Approach 2:
The patent changes the measurement parameter from traditional spectral channels to coded aperture patterns. By transforming the measurement space through coding, the system achieves compressive spectral imaging where fewer measurements are needed compared to the number of spectral elements, improving measurement efficiency while maintaining accuracy.
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 the calculation of spectral images with high optical efficiency and low component and design costs, achieving accurate spectral imaging without the missing cone problem and requiring fewer measurements than the number of elements in the data cube.
Implementation Method 1
A wavelength-dependent shift is created in a first image of electromagnetic energy emanating from the object by imaging the first image through a first dispersive element
Implementation Method 2
The second image is modulated according to a code of the coded aperture
Implementation Method 3
The wavelength-dependent shift in the second image is removed by imaging through the second dispersive element
Data Source
AI summary
Embodiments of the present invention relate to systems and methods for spectral imaging. Electromagnetic energy emanating from an object is passed through a first dispersive element, a coded aperture, and a second dispersive element to a detector plane. A wavelength-dependent shift is created by the first dispersive element. The coded aperture modulates the image emanating from the first dispersive element. The wavelength-dependent shift is removed from the modulated image by the second dispersive element producing a wavelength-independent image measured by the detector. A spectral image of the object is calculated from the measured image, a wavelength-dependent shift of the first dispersive element, the code of the coded aperture, and a wavelength dependent shift of the second dispersive element. A spectral image can be calculated from measurements obtained in a single time step and from a number of measurements that is less than the number of elements in the spectral image.