Compact freeform-surface-based Offner imaging spectrometer with both a long-slit and broadband

Area of Science:

• Optical engineering
• Spectroscopy
• Freeform optics

Background:

• Conventional imaging spectrometers struggle with simultaneous large field of view (FOV), broadband operation, and compact size.
• Achieving these features requires overcoming optical design challenges related to aberrations and system miniaturization.

Purpose of the Study:

• To propose and design a compact freeform-surface-based Offner imaging spectrometer with a long-slit and broadband capabilities (CISLS).
• To address the trade-offs between slit off-axis amount, system compactness, and anastigmatic imaging.

Main Methods:

• Utilized vector aberration theory and analytical studies to understand Zernike polynomial contributions to astigmatism.
• Employed Zernike terms Z5 and Z6 to balance astigmatism for miniaturization, and other terms to correct FOV-dependent astigmatism.
• Designed a freeform-surface-based Offner spectrometer architecture.

Main Results:

• The proposed compact imaging spectrometer with a long-slit (CISLS) achieved a spectral resolution of 2.7 nm.
• The system operates across a broadband range of 400 nm to 1000 nm.
• The spectrometer has a compact volume of 60 mm × 64 mm × 90 mm and a 30 mm long slit.

Conclusions:

• The developed freeform-surface-based Offner imaging spectrometer successfully integrates a large field of view, broadband operation, and a compact structure.
• This design overcomes the limitations of conventional imaging spectrometers, offering a miniaturized solution for advanced spectral imaging applications.