Diffraction Grating Aberration Correction via Local Blaze Wavelength Variation
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Solution Overview
Problem
Conventional spectral devices with diffraction gratings face complexity in manufacturing and correcting aberrations such as spherical, coma, and chromatic aberrations, making it difficult to achieve a simple structure for correction.
Innovation Solution
The diffraction grating is designed with grooves having different blaze wavelengths in various regions to optimize diffraction efficiency, where grooves in one region have a lower efficiency where aberrations are likely to occur and higher efficiency where they are not, allowing for aberration correction with a simple structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the diffraction grating uses a uniform groove structure across the irradiation region, then the manufacturing process is simple, but aberrations such as spherical aberration, coma aberration, and chromatic aberration occur and cannot be corrected
Solution Approach 1:
The patent applies local quality by making the groove depth vary across different regions of the irradiation area. Specifically, the groove depth is set to be different between a first region and a second region, allowing each region to have optimized diffraction characteristics for its specific function, thereby correcting aberrations while maintaining manufacturing feasibility
Solution Approach 2:
The patent changes the physical parameter of groove depth across different regions of the diffraction grating. By varying the groove depth parameter spatially, the diffraction efficiency and blaze wavelength are optimized for different regions, enabling aberration correction without requiring complex manufacturing processes
2Manufacturing precision
If the diffraction grating is designed with multiple regions having different blaze wavelengths to correct aberrations, then aberration correction is achieved, but the manufacturing condition becomes complicated
Solution Approach 1:
The patent divides the irradiation area into multiple regions (first region and second region) with different groove depths, where each region has optimized local diffraction properties. This local optimization allows aberration correction across the entire grating while using a relatively simple manufacturing approach that only requires varying one parameter (groove depth) rather than multiple complex parameters
Solution Approach 2:
The patent segments the irradiation area into distinct regions (first region and second region) with different groove depth characteristics. This segmentation allows independent optimization of each region's diffraction properties, enabling comprehensive aberration correction while maintaining manageable manufacturing complexity through modular regional design
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 approach effectively corrects aberrations in the diffraction grating with a simple structure by varying the blaze wavelengths and depths of grooves, improving resolution and reducing aberrations across different wavelength ranges.
Implementation Method 1
a diffraction grating that diffracts light irradiated onto an irradiation region and spectrally disperses the light into lights of respective wavelengths
Implementation Method 2
multiple grooves for diffracting light are formed in the irradiation region
Implementation Method 3
at least some grooves have a blaze wavelength that is different from that of the other grooves, the blaze wavelength being a wavelength at which a diffraction efficiency peaks
Implementation Method 4
a relationship between a wavelength of light to be spectrally dispersed and a diffraction efficiency differs depending on shapes of the grooves
Data Source
AI summary
An irradiation region 21 of a diffraction grating 2 includes a first irradiation region (21A) and a second irradiation region (21B). In the diffraction grating 2, a blaze wavelength of a groove 22 of the first irradiation region (21A) is different from a blaze wavelength of a groove 23 of the second irradiation region (21B). That is, the first irradiation region (21A) and the second irradiation region (21B) have different relationships between a wavelength of light to be spectrally dispersed and a diffraction efficiency. Therefore, in a spectral device, light on a short wavelength side of light reflected by the second irradiation region (21B) of the diffraction grating 2 is not diffracted and is not received by a detector. Then, in a spectral device 1, aberration on the short wavelength side is corrected. In this way, in the diffraction grating 2, an aberration can be corrected with a simple structure in which the grooves (22, 23) are formed such that the blaze wavelengths in the first irradiation region (21A) and the second irradiation region (21B) are different from each other.