An illumination system, comprising: multiple light emitting elements (LEEs) (212a, 212b; 512a, 512b); a first light guide (230a; 430a; 530a; 630a) extending along a first plane, the first light guide being positioned and arranged to receive light from at least some of the LEEs and guide the light in a first direction in the first plane as first guided light, wherein the first light guide forms a single first exit aperture at one end through which the first guided light exits the first light guide; a second light guide (230b; 430b; 530b; 630b) extending along the first plane, the second light guide being positioned and arranged to receive light from at least some other of the LEEs and guide the light in a second direction in the first plane opposite to the first direction as second guided light, wherein the second light guide forms a single second exit aperture at one end through which the second guided light exits the second light guide; a first redirecting optic (240a; 440a; 540a; 640a) positioned and arranged to receive the first guided light from the first light guide through the single first exit aperture and direct the light in a first angular range (142a, 142b) and a second angular range; and a second redirecting optic (240b; 440b; 540b; 640b) positioned and arranged to receive the second guided light from the second light guide through the single second exit aperture and direct the light in a third angular range and a fourth angular range (142a', 142b'), wherein the first, second, third and fourth angular ranges are different, wherein the illumination system is configured so that: the light in the first angular range is output as first output light having a prevalent direction with a non-zero component parallel to a direction which is orthogonal to the first plane; the light in the third angular range is output as third output light having a prevalent direction with a non-zero component parallel to the direction which is orthogonal to the first plane; the light in the second angular range is output as second output light having a prevalent direction with a non-zero component antiparallel to the direction which is orthogonal to the first plane; and the light in the fourth angular range is output as fourth output light having a prevalent direction with a non-zero component antiparallel to the direction which is orthogonal to the first plane. multiple light emitting elements (LEEs) (212a, 212b; 512a, 512b); a first light guide (230a; 430a; 530a; 630a) extending along a first plane, the first light guide being positioned and arranged to receive light from at least some of the LEEs and guide the light in a first direction in the first plane as first guided light, wherein the first light guide forms a single first exit aperture at one end through which the first guided light exits the first light guide; a second light guide (230b; 430b; 530b; 630b) extending along the first plane, the second light guide being positioned and arranged to receive light from at least some other of the LEEs and guide the light in a second direction in the first plane opposite to the first direction as second guided light, wherein the second light guide forms a single second exit aperture at one end through which the second guided light exits the second light guide; a first redirecting optic (240a; 440a; 540a; 640a) positioned and arranged to receive the first guided light from the first light guide through the single first exit aperture and direct the light in a first angular range (142a, 142b) and a second angular range; and a second redirecting optic (240b; 440b; 540b; 640b) positioned and arranged to receive the second guided light from the second light guide through the single second exit aperture and direct the light in a third angular range and a fourth angular range (142a', 142b'), wherein the first, second, third and fourth angular ranges are different, wherein the illumination system is configured so that: the light in the first angular range is output as first output light having a prevalent direction with a non-zero component parallel to a direction which is orthogonal to the first plane; the light in the third angular range is output as third output light having a prevalent direction with a non-zero component parallel to the direction which is orthogonal to the first plane; the light in the second angular range is output as second output light having a prevalent direction with a non-zero component antiparallel to the direction which is orthogonal to the first plane; and the light in the fourth angular range is output as fourth output light having a prevalent direction with a non-zero component antiparallel to the direction which is orthogonal to the first plane. the light in the first angular range is output as first output light having a prevalent direction with a non-zero component parallel to a direction which is orthogonal to the first plane; the light in the third angular range is output as third output light having a prevalent direction with a non-zero component parallel to the direction which is orthogonal to the first plane; the light in the second angular range is output as second output light having a prevalent direction with a non-zero component antiparallel to the direction which is orthogonal to the first plane; and the light in the fourth angular range is output as fourth output light having a prevalent direction with a non-zero component antiparallel to the direction which is orthogonal to the first plane.