Multi-Grating Spectrometer with Convex Polygon Arrangement
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Solution Overview
Problem
Diffraction grating spectrometers face limitations in resolving power and high light intensity losses due to the need for large gratings, which increase costs and reduce precision in spectral measurement.
Innovation Solution
A spectrometer design utilizing multiple diffraction gratings arranged in a convex polygon configuration, where a portion of the light beam is diffracted multiple times by each grating, enhancing resolving power without increasing grating size or cost, and minimizing light intensity losses by direct optical paths between gratings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the width of the incident light beam and consequently the dimensions of the diffraction grating are increased, then the resolving power is improved, but the cost of the diffraction grating increases
Solution Approach 1:
The patent divides the spectral dispersion function into multiple segments by using several diffraction gratings (at least three) arranged in sequence. Each grating contributes to the overall resolving power, so that the sum of resolving powers from individual gratings achieves the desired total resolving power without requiring a single large expensive grating. This segmentation allows cost reduction while maintaining measurement precision.
Solution Approach 2:
The patent combines multiple diffraction gratings into a single optical path system where light passes through each grating sequentially. The resolving powers of individual gratings are merged to achieve the total resolving power of the system. This combining approach replaces the need for one large expensive grating with multiple smaller, more affordable gratings that work together to provide the required spectral resolution.
2Measurement precision
If the dimensions of the diffraction grating are increased, then the resolving power is improved, but the size of the spectrometer increases
Solution Approach 1:
The patent segments the spectral dispersion function across multiple smaller diffraction gratings arranged in sequence. Each grating has reduced dimensions compared to a single large grating, so the overall volume of the spectrometer is reduced while the cumulative resolving power remains sufficient for the application. The gratings are positioned to minimize space occupation while maintaining optical efficiency.
Solution Approach 2:
The patent transitions from a single large grating approach to a multi-grating sequence approach, utilizing the temporal/dimensional sequence of light passage through multiple gratings. This dimensional change from spatial size to sequential arrangement allows achieving high resolving power without proportionally increasing the physical volume of the instrument.
3Device complexity
If a single diffraction grating is used, then the device complexity is low, but the light intensity losses are high
Solution Approach 1:
The patent introduces intermediate optical elements (at least two mirrors) between the diffraction gratings to guide and redirect the light beam. These intermediaries enable the light to pass through multiple gratings in sequence while maintaining efficient optical paths and minimizing intensity losses. The mirrors act as mediators that connect the gratings without causing additional energy loss, allowing the system to achieve high resolving power while maintaining adequate light intensity.
4Measurement precision
If multiple diffraction gratings are used, then the resolving power is improved, but the device complexity increases
Solution Approach 1:
The patent designs the multi-grating system where each diffraction grating serves multiple functions: spectral dispersion, wavelength selection, and contribution to overall resolving power. The mirrors between gratings also serve dual purposes of beam redirection and optical path management. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity while achieving high resolving power.
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 design achieves high resolving power comparable to larger spectrometers at a lower cost, with reduced light intensity losses, allowing for precise spectral measurement and reduced size, facilitating better wavelength determination than traditional methods.
Implementation Method 1
The diffraction grating has reflective bands or lines, periodically arranged parallel to the axis (Oz) of the orthonormal frame (Oxyz) and in the plane (xOz). The period defining the arrangement of the reflective bands is a length called the grating pitch.
Implementation Method 2
A light beam 11 is incident on the diffraction grating 10. It forms an angle i with the normal 13 to the plane of the grating 10. The light beam 11 is monochromatic, of wavelength λ 0. It is returned by the diffraction grating in the form of several sub-beams: a specular sub-beam 12, corresponding to a diffraction of order 0 or in other words to a specular reflection
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention relates to a spectrometer (20) comprising: means (22) for spectrally dispersing an initial light beam (240); and a photodetector (21). According to the invention, the spectrally dispersing means (22) comprise at least three reflective diffraction gratings (201, 202, 203) parallel to consecutive sides of a convex polygon (23), said sides being arranged so that a portion of the initial light beam (240) is diffracted alternately by each of the diffraction gratings (201, 202, 203) and is diffracted at least a second time by at least one of the diffraction gratings (201).