Abstract: A pair of optical beams of radiant energy from separate paths in a spectrophotometer are coaxially merged into a single composite beam with an optical member which resembles a coarse echelette grating. A reflective surface which includes the surfaces of sidewalls within a plurality of parallel grooves is disposed on the optical member. The grooves are arranged in a lateral array and are generally V-shaped cross-sectionally. The beams to be combined are directed upon the sidewalls and the composite beam is emitted therefrom in accordance with the law of reflection. When the beams to be combined include non-collimated rays, shadowing is provided by the portion of the optical member between adjoining sidewalls of adjacent grooves to reduce flare. Furthermore, image aberrations as caused by off-axis operation due to use of a spherical mirror in the beam combining arrangement, are substantially corrected by the optical member.