VNIR Spectrometer with Concave Grating for Uniform Resolution
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Spectrometers face challenges in achieving high and uniform spectral resolution across their spectral range while being compact and cost-effective, with existing designs often showing a 'U' shaped curve in spectral resolution versus wavelength plots and varying performance at different wavelengths.
Innovation Solution
A spectrometer design featuring a concave diffraction grating with a Littrow configuration and adjustable light source mount, which allows for precise adjustment of the light source's distance, orientation, and position to optimize the angle of incidence and out-of-plane angle between 5 to 8 degrees and 1.5 to 4 degrees respectively, combined with a correcting lens and order sorting filter to enhance spectral resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional spectrometer design is used, then the spectral resolution varies significantly across the spectral range (U-shaped curve), but the device complexity and cost are reduced
Solution Approach 1:
The patent applies parameter changes by optimizing the angle of incidence (5 to 8 degrees) and out-of-plane angle (1.5 to 4 degrees) of the light beam relative to the diffraction grating's axis of normal incidence. These specific angular parameters transform the conventional U-shaped spectral resolution curve into a substantially flat response across the spectral range, achieving uniform spectral resolution below 5 nm from 400 nm to 850 nm without requiring complex additional optical elements
Solution Approach 2:
The patent employs a concave diffraction grating with a specific radius of curvature (R = 75 mm) to achieve both dispersion and focusing functions. The curved surface of the grating enables it to act as both a dispersing element and a focusing element, eliminating the need for separate correcting lenses and simplifying the optical system while maintaining uniform spectral resolution across the detection range
2Measurement precision
If the spectral range is extended, then the spectral resolution decreases at the wavelength limits, but the useful detection range is increased
Solution Approach 1:
The patent uses parameter changes by optimizing the diffraction grating parameters (groove density, blaze angle) and the incident angles to achieve a balance between spectral range and resolution. The specific angular parameters (5-8 degrees in-plane, 1.5-4 degrees out-of-plane) enable the system to maintain spectral resolution below 5 nm across an extended range from 400 nm to 850 nm, overcoming the conventional degradation at wavelength limits
3Device complexity
If compact and cost-effective design is prioritized, then additional correcting elements are removed, but the spectral resolution uniformity deteriorates
Solution Approach 1:
The patent applies universality by designing the concave diffraction grating to perform multiple functions simultaneously: dispersion of light into different wavelengths and focusing of the diffracted light onto the detector. This multi-functional design eliminates the need for separate correcting lenses or mirrors, reducing the number of optical elements while maintaining uniform spectral resolution across the spectral range
Solution Approach 2:
The concave (curved) surface of the diffraction grating enables it to provide both angular dispersion and spatial focusing in a single element. The specific radius of curvature (R = 75 mm) is optimized to achieve uniform spectral resolution without requiring additional correcting optical elements, thus simplifying the overall instrument design while maintaining measurement precision
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 improved spectral resolution with minimal variation across the spectral range, reducing the spectral resolution to below 5 nm over 95% of the range and maintaining high performance from 400 nm to 850 nm, while maintaining a compact and cost-effective structure.
Implementation Method 1
a diffraction grating configured to receive a light beam from the light source and to disperse the light beam to form a dispersed light beam
Data Source
AI summary
A spectrometer is disclosed, comprising: a light source configured to receive light from a scene; a diffraction grating configured to receive a light beam from the light source and to disperse the light beam to form a dispersed light beam, the diffraction grating comprising an axis of normal incidence and a plurality of grooves, these defining a plane that includes the axis of normal incidence and which is normal to the grooves; a detector configured to detect the dispersed light beam; wherein the angle of incidence, between the light beam and the axis of normal incidence in the plane, is 5 to 8 degrees, and the out-of-plane angle, between the light beam and the axis of normal incidence outside the plane is 1.5 to 4 degrees. A correcting lens may be provided, disposed between the diffraction grating and the detector.