Optical Design and Wavelength Calibration of a DMD-based Multi-Object Spectrograph

TL;DR

This paper presents the optical design, wavelength calibration, and preliminary testing of a DMD-based multi-object spectrograph for astronomical observations, demonstrating its potential for high-throughput, programmable spectroscopy.

Contribution

It introduces a novel DMD-based spectrograph design with optimized optics and calibration procedures, advancing the application of digital micromirror devices in astronomy.

Findings

Designed a DMD-MOS covering 0.4-0.7 μm with R~1000

Developed a wavelength calibration procedure using simulated data

Explored the relationship between micromirrors and detector pixels

Abstract

The multi-object spectrograph (MOS) has been the benchmark for the current generation of astronomical spectrographs, valued for its ability to acquire the spectra of hundreds of objects simultaneously. In the last two decades, the digital micromirror device (DMD) has shown potential in becoming the central component of the MOS, being used as a programmable slit array. We have designed a seeing-limited DMD-based MOS covering a spectral range of 0.4 to 0.7 $\mu$m, with a field of view (FOV) of $10.5^\prime \times 13.98^\prime$ and a spectral resolution of $R\sim1000$. This DMD-MOS employs all-spherical refractive optics, and a volume phase holographic (VPH) grism as the dispersive element for high throughput. In this paper, we present the optical design and optimization process of this DMD-MOS, as well as a preliminary wavelength calibration procedure for hyperspectral data reduction. Using simulated data of the DMD-MOS, a procedure was developed to measure hyperspectral imaging distortion and to construct pixel-to-wavelength mappings on the detector. An investigation into the relationships between DMD micromirrors and detector pixels was conducted. This DMD-MOS will be placed on a 0.5 m diameter telescope as an exploratory study for future DMD-based MOS systems.