A light combining system comprising: a first prism comprising a first entrance face enabled to receive first on-state light from a first DMD; a second prism, facing the first prism, comprising a second entrance face enabled to receive second on-state light from a second DMD; at least one interface between the first prism and the second prism enabled to receive the first on-state light and the second on-state light; a mirror at the at least one interface, enabled to transmit the first on-state light, crossing the first prism, through the second prism and reflect the received second on-state light in alignment with the first on-state light back through the second prism, each of respective angles formed by a normal of the mirror and each of the first on-state light and the second on-state light being less than a total internal reflection angle of the corresponding either first prism or second prism; a combination of respective back working distances of the first DMD and the second DMD from the corresponding first prism and second prism and respective shapes of each of the first prism and the second prism chosen such that: respective illumination paths and respective reflection paths of each of the first DMD and the second DMD do not interfere with each other; and, the respective illumination paths do not intersect the first prism and the second prism, and respective off-state paths of the first DMD and the second DMD do not intersect the first prism and the second prism. a first prism comprising a first entrance face enabled to receive first on-state light from a first DMD; a second prism, facing the first prism, comprising a second entrance face enabled to receive second on-state light from a second DMD; at least one interface between the first prism and the second prism enabled to receive the first on-state light and the second on-state light; a mirror at the at least one interface, enabled to transmit the first on-state light, crossing the first prism, through the second prism and reflect the received second on-state light in alignment with the first on-state light back through the second prism, each of respective angles formed by a normal of the mirror and each of the first on-state light and the second on-state light being less than a total internal reflection angle of the corresponding either first prism or second prism; a combination of respective back working distances of the first DMD and the second DMD from the corresponding first prism and second prism and respective shapes of each of the first prism and the second prism chosen such that: respective illumination paths and respective reflection paths of each of the first DMD and the second DMD do not interfere with each other; and, the respective illumination paths do not intersect the first prism and the second prism, and respective off-state paths of the first DMD and the second DMD do not intersect the first prism and the second prism. respective illumination paths and respective reflection paths of each of the first DMD and the second DMD do not interfere with each other; and, the respective illumination paths do not intersect the first prism and the second prism, and respective off-state paths of the first DMD and the second DMD do not intersect the first prism and the second prism.