Single-Pixel IR Hadamard Spectrometer With Self-Calibration
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Solution Overview
Problem
Existing infrared spectrometers, particularly those operating in the mid-infrared range, are hindered by size, cost, and sensitivity to external disturbances, making them unsuitable for field applications. Current technologies such as FTIR, dispersive, and compressive sensing spectrometers face challenges in miniaturization and real-time imaging due to mechanical complexity, high cost, or spectral range limitations.
Innovation Solution
A single-pixel infrared Hadamard transform spectrometer with a moveable encoding mask and cascaded encoding regions, utilizing a 635 nm laser for self-calibration, reduces mechanical complexity and size while maintaining spectral resolution, allowing for compact and cost-effective field use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a FTIR spectrometer is used, then spectral resolution and wavelength sensing range are improved, but device complexity and sensitivity to external disturbances increase
Solution Approach 1:
The patent replaces the mechanical moving mirror system of FTIR with a static diffraction grating and a single-pixel detector system. The spectral information is encoded spatially on the detector plane rather than being measured through mechanical scanning, eliminating sensitivity to external disturbances while maintaining spectral resolution through computational reconstruction.
Solution Approach 2:
The patent uses a single-pixel detector to capture encoded spectral information multiple times with different encoding patterns. Each measurement is a 'copy' of the spectral information encoded differently, and these copies are computationally combined to reconstruct the full spectrum, replacing the need for mechanical scanning.
2Measurement precision
If array detectors are used in IR dispersive spectrometers, then spectral detection capability is improved, but device size and cost increase
Solution Approach 1:
The patent segments the spectral information capture process into multiple sequential measurements with different encoding patterns applied at the diffraction grating. Instead of using a large array detector to capture all spectral information simultaneously, the system uses a single-pixel detector to capture encoded information in segments, which are then computationally reconstructed into the full spectrum.
Solution Approach 2:
The patent transforms the spectral measurement from a spatial array detection problem into a temporal sequence of single-pixel measurements. Spectral information is encoded in the spatial distribution of light at different angles, which is then captured sequentially over time through angular scanning, converting a two-dimensional spatial detection problem into a one-dimensional temporal measurement process.
3Loss of time
If compressive sensing encoding is used, then measurement number is reduced, but computational time and image quality deteriorate
Solution Approach 1:
The patent changes the encoding parameter from random patterns used in compressive sensing to structured orthogonal Hadamard patterns. This parameter change in the encoding scheme allows for perfect reconstruction of spectral information with fewer measurements while maintaining high signal-to-noise ratio and avoiding the computational complexity and image quality degradation associated with compressive sensing.
4Measurement precision
If a moving encoding mask is used in HT spectrometer, then spectral encoding is achieved, but mechanical complexity and size increase
Solution Approach 1:
The patent replaces the mechanically complex moving encoding mask with a static diffraction grating that performs spectral encoding through diffraction. The encoding function previously requiring mechanical movement of a mask is achieved here through the fixed geometric structure of the grating, eliminating mechanical complexity while maintaining spectral encoding capability.
Solution Approach 2:
The patent introduces a diffraction grating as an intermediary element that performs the spectral encoding function. Instead of directly moving an encoding mask to modulate light, the grating acts as a mediator that spatially encodes spectral information through diffraction angles, which are then captured by the single-pixel detector through angular scanning.
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 spectrometer achieves accurate mid-IR spectroscopy with increased signal-to-noise ratio, enabling miniaturization and cost-effectiveness, suitable for field applications in environmental monitoring, pharmaceutics, and agriculture.
Implementation Method 1
a dispersion and imaging optics disposed between the entrance slit and the moveable encoding mask for dispersing the infrared signal and for imaging the dispersed infrared signal onto the moveable encoding mask
Implementation Method 2
a first single pixel detector sensitive to infrared light in a first spectral range
Data Source
AI summary
Infrared spectrometer and method of performing infrared spectrometry. In one embodiment, the method comprises the steps of providing a first single pixel detector sensitive to infrared light in a first spectral range; providing an entrance slit for receiving an infrared light signal; disposing a moveable encoding mask between the entrance slit and the first single pixel detector for encoding based multiplexing, the moveable encoding mask comprising at least three adjacent coding sections along an encoding moving direction thereof, each coding section comprising the same coding pattern in a cyclic manner such that a last encoding step of one encoding section is the same as a first encoding step in a next encoding section step; disposing a dispersion and imaging optics between the entrance slit and the moveable encoding mask for dispersing the infrared signal and for imaging the dispersed infrared signal onto the moveable encoding mask; disposing a collection optics between the moveable encoding mask and the first single pixel detector for collecting an encoding based multiplexed version of the infrared signal onto the first single pixel photodetector; selectively allowing only one of at least first and second bands within the first spectral range to be imaged onto respective ones of the coding sections excluding a first coding section along the encoding moving direction of the moveable encoding mask, in a starting position of the moveable encoding mask; and moving the moveable encoding mask in the encoding moving direction for the encoding based multiplexing.