<p>In an embodiment, an apparatus includes a module assembly and a main assembly. The module assembly includes a module assembly housing, a first face plate and an analysis unit attached to the first face. The main assembly includes a main assembly housing, a second face plate and an engine unit rigidly attached to the second face plate. The engine unit generates a light that passes to the analysis unit via a first lens assembly and a second lens assembly. The first lens assembly is attached to the first face plate and the second lens assembly is attached to the second face plate. The module assembly when attached to the main assembly causes the first and second face plates to act as a single mechanical unit that moves independent of movement of the module assembly housing and/or the main assembly housing.</p>
