Methods and apparatuses for aligning and diagnosing the laser beam traversing an optical train in a highly space-efficient, lower cost and/or retrofit-friendly manner are disclosed. The optical components of the optical train are mounted such that one or more optical components can direct their exit laser beam to partially or wholly scan across one or more downstream sensors. Correlation data between physical disposition of optical components and the points of impact data and/or beam quality data are employed to, among others, align and/or diagnose the laser beam and/or localize failure sites and/or optimize maintenance schedule.