A flame scanner includes a lens barrel assembly defining a generally hollow body having a first end and a second end, and an opening formed in the first end, a lens positioned adjacent to the second end, and a fiber optic cable receivable through the opening in the first end, the fiber optic cable having a distal end. A field of view of the flame scanner is selectively adjustable by varying a position of the distal end of the fiber optic cable with respect to the lens.