Three-Channel Gas Detection Spectrometer with Shared Optics
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Solution Overview
Problem
Existing spectrometers require multiple channels to detect narrow spectral lines, leading to increased size, weight, cost, and complexity due to the need for multiple slits, gratings, and focal plane arrays, which results in inefficient throughput and calibration challenges.
Innovation Solution
A three-channel spectrometer design that integrates all spectral bands into a single optical system with a single diffraction grating and focal plane array, using a common optical form and slits, which reduces hardware redundancy and improves alignment and calibration, allowing for high spectral resolution detection of three narrow bands within a single instrument.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If three separate spectrometers with three slits, three collimators, three gratings, three imaging systems, and three FPAs are used to detect three spectral lines, then the spectral detection capability is improved, but the device complexity, size, weight, and cost increase significantly
Solution Approach 1:
The patent merges three separate spectrometer channels into a single integrated instrument by combining three slits, one common optical system, one diffraction grating, and one focal plane array with three million detectors. This integration maintains the capability to detect three different spectral lines (oxygen at 0.76 microns, carbon dioxide at 1.61 and 2.06 microns) while eliminating the need for triplicated optical components, thereby reducing device complexity, size, weight, and cost
Solution Approach 2:
The common optical system and single diffraction grating serve multiple functions by handling all three spectral bands simultaneously. The single focal plane array with three million detectors processes all three spectral channels, making the system universal rather than requiring separate dedicated components for each spectral line detection
2Measurement precision
If three separate spectrometers with triplicated hardware are used, then the spectral resolution requirement is met, but the size and weight of the instrument increase
Solution Approach 1:
The patent combines three separate spectrometer systems into one integrated instrument that achieves spectral resolution of 20,000 λ/Δλ for all three spectral lines simultaneously. By sharing common components (optical system, grating, imaging system, and FPA), the instrument weight is dramatically reduced compared to having three separate spectrometers while maintaining the required high spectral resolution for gas detection
3Adaptability or versatility
If three separate spectrometers with multiple gratings positioned at eighteen degrees off Littrow condition are used, then the spectral lines are detected, but the throughput decreases due to increased shadowing
Solution Approach 1:
The patent changes the operational parameter of the diffraction grating from being positioned at eighteen degrees off the Littrow condition to being positioned at only a few degrees off the Littrow condition. This parameter change reduces shadowing effects and increases optical throughput for all three spectral bands while maintaining the capability to detect the narrow spectral lines at high resolution
4Adaptability or versatility
If three million detectors are purchased for three separate FPAs, then all spectral channels are covered, but only 0.6 million detectors are actually used resulting in waste
Solution Approach 1:
The patent merges three separate focal plane arrays into a single FPA with three million detectors that handles all three spectral channels. This integration ensures that all purchased detectors are utilized effectively across the different spectral bands, eliminating the waste that would occur with separate FPAs where only a fraction of detectors are used. The single FPA design optimizes detector utilization while maintaining full spectral coverage
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 design simplifies the spectrometer, reduces size and weight, enhances throughput, and achieves high spectral resolution with fewer detectors used, while maintaining high efficiency and ease of calibration, achieving spectral resolution of approximately 17,000 to 20,000 λ/Δλ.
Implementation Method 1
a first dichroic beamsplitter, which reflects a first portion of the radiation and transmits a portion of the radiation. The transmitted portion is incident on a second dichroic beamsplitter, which reflects a second portion of the radiation and transmits a third portion
Implementation Method 2
a dispersive element that receives and reflects the collimated first, second, and third slit output radiation from the optical form
Implementation Method 3
a single diffraction grating
Data Source
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AI summary
A three-channel spectrometer including: a beamsplitter element that receives an incident radiation and transmits a first portion, a second portion, and a third portion of the incident radiation, a first slit that receives the first portion and transmits a first slit output radiation of a first wavelength range; a second slit that receives the second portion and transmits a second slit output radiation of a second wavelength range; a third slit that receives the third portion of the incident radiation and transmits a third slit output radiation of a third wavelength range; a common optical form that receives and collimates the first, second, and third slit output radiation; and a dispersive element that receives and reflects the collimated first, second, and third slit output radiation from the optical form.