Hadamard transform spectrometer 

https://doi.org/10.1351/goldbook.08253
Multiplexing spectrometer that uses the optical components of a dispersive spectrometer with a Hadamard encoding mask.
Source:
PAC, 2021, 93, 647. 'Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)' on page 661 (https://doi.org/10.1515/pac-2019-0203)