A design method for direct vision coaxial linear dispersion spectrometers.

Area of Science:

• Optics and Photonics
• Spectroscopy
• Optical Engineering

Background:

• Prism and grating spectrometers suffer from significant nonlinear dispersion, limiting their accuracy.
• Existing dispersive spectrometers require complex correction methods to achieve linear spectral output.
• Nonlinear dispersion leads to spectral distortions, affecting measurement precision.

Purpose of the Study:

• To propose and validate a novel spectrometer design method using a prism-prism-grating (PPG) dispersion module.
• To achieve highly linear spectral dispersion, correcting for the inherent nonlinearities of traditional designs.
• To demonstrate the effectiveness of the PPG module in enhancing spectrometer performance.

Main Methods:

• Analysis of dispersion characteristics of prisms and gratings to select optimal optical materials for the PPG module.
• Application of a loop traversal algorithm for optimizing system structure parameters.
• Derivation of the direct vision coaxial condition for the PPG module based on optical principles.
• Establishment of a spectral linearity index using the PPG module's dispersion equation.
• Design and realization of a direct vision coaxial linear dispersion spectrometer within the 400-990 nm band.

Main Results:

• A direct vision coaxial linear dispersion spectrometer was successfully designed and realized.
• The spectrometer operates in the 400-990 nm band with zero deviation angle and offset for a 695 nm central wavelength.
• Simulations confirm theoretical calculations, showing spectral resolution <1.5 nm and spectral smile/keystone <3.89% pixels.
• The design method's universality was verified for 1000-1600 nm and 1600-2200 nm bands.

Conclusions:

• The proposed prism-prism-grating (PPG) dispersion module effectively corrects nonlinear dispersion in spectrometers.
• The developed design method enables the creation of direct vision coaxial linear dispersion spectrometers with high accuracy.
• The PPG spectrometer offers advantages over other dispersion structures and demonstrates broad applicability across different spectral bands.