  The ongoing development of large infrared array detectors has enabled wide
field, deep surveys to be undertaken. There are, however, a number of
challenges in building an infrared instrument which has both excellent optical
quality and high sensitivity over a wide field. We discuss these problems in
the context of building a wide field imaging camera for the 3.5m telescope at
Calar Alto with the new 2K*2K HgCdTe HAWAII-2 focal plane array. Our final
design is a prime focus camera with a 15' field-of-view, called Omega 2000. To
achieve excellent optical quality over the whole field, we have had to dispense
with the reimaging optics and cold Lyot stop. We show that creative baffling
schemes, including the use of undersized baffles, can compensate for the lost K
band sensitivity. A moving baffle will be employed in Omega 2000 to allow full
transmission in the non-thermal J and H bands.
