Echelle Spectrometer Internal Predispersion for Order Separation
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Solution Overview
Problem
Echelle spectrometers with internal order separation face challenges in detecting large spectral ranges with high resolution and sufficient light throughput, especially when radiation sources have varying spectral intensities, as existing detectors often lack sufficient dynamic range, leading to compromised sensitivity or separate detection of spectral ranges.
Innovation Solution
The Echelle spectrometer assembly incorporates a predispersing element and imaging optical assembly to generate an additional image plane, allowing for manipulation of radiation density using optical means like a grey filter or prism, ensuring even intensity distribution across the detector and optimizing detector usage by compensating for intensity variations and spectral distributions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large spectral range is detected with high resolution, then measurement precision is improved, but detector area must be very large which increases device complexity and cost
Solution Approach 1:
The patent applies predispersion in a direction lateral to the main dispersion direction, creating a two-dimensional spectrum on the detector. This dimensional approach allows the spectral range to be expanded without proportionally increasing the detector area, as the predispersion effectively multiplies the usable spectral information within the detector's physical boundaries.
Solution Approach 2:
The predispersing element is positioned before the Echelle grating to pre-separate the spectrum in the lateral direction. This preliminary dispersion action ensures that when the radiation passes through the Echelle grating, the orders are already partially separated, reducing the need for large detector area to capture the full spectral range with high resolution.
2Productivity
If spectral ranges with different intensities are detected simultaneously, then productivity is improved, but detector dynamic range is insufficient causing saturation or compromised sensitivity
Solution Approach 1:
The patent introduces optical means (such as variable neutral density filters or spatial filters) that can locally adjust the intensity distribution across different spectral regions on the detector. This allows strong spectral ranges to be attenuated while preserving weak ranges, enabling simultaneous detection across the entire spectral range without saturation or loss of sensitivity.
Solution Approach 2:
The system employs dynamic intensity control mechanisms that can adjust the radiation density distribution in real-time. This dynamic adjustment allows the detector to handle spectra with widely varying intensities by adapting the intensity distribution to match the detector's dynamic range capabilities.
3Measurement precision
If lateral dispersion is increased to completely separate orders, then measurement precision is improved, but unused space between orders increases reducing light throughput
Solution Approach 1:
By applying predispersion before the Echelle grating, the system pre-separates spectral orders in the lateral direction. This preliminary action allows for more efficient use of the detector area and reduces the amount of unused space between orders, thereby improving light throughput while maintaining high spectral resolution.
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 solution enables simultaneous detection of large spectral ranges with high resolution and even intensity distribution, effectively utilizing commercially available detectors and preventing saturation, while maintaining high light throughput and accurate spectral measurement.
Implementation Method 1
predispersion means for predispersion of radiation in the direction of the lateral dispersion of the dispersing element
Implementation Method 2
an Echelle grating for the spectral separation of radiation in a main dispersion direction
Implementation Method 3
gratings are used which have a stairs-shaped (Echelle (French=stairs) cross section. By the stepped structure with a suitable Blaze angle a diffraction pattern is generated
Implementation Method 4
a dispersing element for the separation of the orders by means of the spectral separation of the radiation in a lateral dispersion direction
Implementation Method 5
an imaging optical assembly for imaging the radiation entering into the spectrometer assembly through an entrance slit in an image plane
Data Source
AI summary
An Echelle spectrometer arrangement (10) with internal order separation contains an Echelle grating (34) and a dispersing element (38) for order separation so that a two-dimensional spectrum having a plurality of separate orders (56) can be generated, an imagine optical system (18, 22, 28, 46), a flat-panel detector (16), and predispersion means (20) for predispersing the radiation into the direction of traverse dispersion of the dispersion element (38). The arrangement is characterized in that the predispersion means (20) comprise a predispersion element which is arranged along the optical path behind the inlet spacing (12) inside the spectrometer arrangement. The imaging optical system is designed in such a manner that the predispersed radiation can be imaged onto an additional image plane (24) which does not have any boundaries in the predispersion direction and which is arranged along the optical path between the predispersion element (20) and the echelle grating (34). Optical means (20, 68) in the area of the predispersed spectrum are arranged to influence the spatial and/or the spectral beam density distribution on the detector (16).