A compact optical arrangement splits the field of view of an upwardly-looking imager into a plurality of intersecting subfields along which return light from a target passes through and past an upright window to the imager. A top mirror is positioned along a vertical axis directly above the imager. Overhead mirror portions located between the imager and the top mirror are spaced radially apart to enable the return light reflected by the top mirror to bypass the overhead mirror portions and pass unobstructedly directly to the imager along a central subfield. A plurality of side fold mirrors reflects the return light passing through the upright window to the overhead mirror portions. The overhead mirror portions are positioned apart to enable the return light reflected by the side fold mirrors to pass to the imager along a pair of outer subfields.