Proceedings of SPIE
The throughput of a Hadamard spectrometer is directly proportional to the length of the slits. However, optical aberrations limit the slit length that can be used. The usable length of curved and straight slits are theoretically and experimentally compared for a typical singly-encoded Hadamard spectrometer that has a Czerny-Turner plane-grating mounting. For this Hadamard spectrometer the optical throughput can be increased by a factor of ten by using properly curved slits.
Esplin, Roy W., "Use of Curved Slits to Increase the Throughput of a Hadamard Spectrometer" (1979). Space Dynamics Lab Publications. Paper 44.