A washer assembly includes a threaded fastener head engaging portion and a surface engaging portion. The projection lens unit, the color separating optical system, the illuminating optical system and the light source power supply are arranged in that order. Sensors are stably attached, preferably via covalent or ionic bonds, to a surface within the device, such as the surface of the excitation source that is exposed to the sample. The mounting portion is electronically fixed to the main circuit board. A locking arrangement is carried by the housing. Isolation may exist between different application andor different threads or virtual machines of the same application.