A monolithic refractory ceramic tube sheet for use in all-ceramic air-to-air indirect heat exchangers, the heat exchanger used in all temperature and all pressure applications. A signal caught by the detecting portion is transmitted through a wire to a substrate portion arranged outside the frame. A stride length, heading, and separation distance between the first and second movable parts are computed based on the determined distances and the location of the mobile object is determined based on the computed stride length, heading, and separation distance. The individual planar laser illumination beam components produced from each PLIM are optically combined to produce a composite substantially planar laser illumination beam having substantially uniform power density characteristics over the entire spatial extend thereof and thus the working range of the system.