This paper presents a systematic discussion of the optical and mechanical tolerances which must be addressed in
order for a laser beam shaper system to perform close to the design criteria. First, a general relationship based
on the intensity law of geometrical optics is presented, which relates the input and output beam profiles, and
particular attention is given to the common Gaussian input beam profile. Next, the impact of collimation errors of
the input beam is addressed. Then, lens mounting errors for a two-lens laser beam shaper are addressed including
lens spacing, decenter, and tilt tolerances. Overall, this paper addresses actual variations of the deterministic
transformation of an input irradiance profile into an output beam profile, whether it employs refractive, reflective
or diffractive optical elements.