  Liger is a next-generation near-infrared imager and integral field
spectrograph (IFS) for the W.M. Keck Observatory designed to take advantage of
the Keck All-Sky Precision Adaptive Optics (KAPA) upgrade. Liger will operate
at spectral resolving powers between R$\sim$4,000 - 10,000 over a wavelength
range of 0.8-2.4$\mu$m. Liger takes advantage of a sequential imager and
spectrograph design that allows for simultaneous observations between the two
channels using the same filter wheel and cold pupil stop. We present the design
for the filter wheels and pupil mask and their location and tolerances in the
optical design. The filter mechanism is a multi-wheel design drawing from the
heritage of the current Keck/OSIRIS imager single wheel design. The Liger
multi-wheel configuration is designed to allow future upgrades to the number
and range of filters throughout the life of the instrument. The pupil mechanism
is designed to be similarly upgradeable with the option to add multiple pupil
mask options. A smaller wheel mechanism allows the user to select the desired
pupil mask with open slots being designed in for future upgrade capabilities.
An ideal pupil would match the shape of the image formed of the primary and
would track its rotation. For different pupil shapes without tracking we model
the additional exposure time needed to achieve the same signal to noise of an
ideal pupil and determine that a set of fixed masks of different shapes
provides a mechanically simpler system with little compromise in performance.
