The illuminators generally provide an air or convection cooling mechanism for the internal bulb to increase its life span and to keep the housing as cool as possible. Unfortunately, direct light from this high intensity source can result in heat absorption by an object positioned on the microscope stage. Light from the quartz-halogen bulb is directed onto the microscope stage by the flexible fiber optic light pipes or guides that can be positioned in an almost infinite number of different configurations. These guides are quite helpful in solving the heat problem, because their internal optical fibers transmit primarily visible illumination with minimal transmission in the near infrared or near ultraviolet spectrum. The result is an intense illumination centered in the visible light spectrum without the associated infrared heat output that can alter or damage either the specimen or the microscope itself.
Light intensity is controlled by a potentiometer housed on the faceplate of the illuminator.
The voltage delivered to the lamp can be varied with the potentiometer in ranges from zero current to 120 volts in continuous increments. Light emitted from the quartz-halogen light source has a constant color temperature that remains at 3200K throughout the adjustable voltage range, producing a very stable illumination source. Optical fibers in the light pipes are terminated at the end of the pipes and produce a large, diffuse cone of light. We have measured the illumination intensity of the QX3 microscope body and stage illuminators for the purposes of comparison to the auxiliary external quartz-halogen illuminator. The QX3 body illuminator produces light measuring approximately 0.0165 lumens, while the substage lamp emits less light that we have measured to be approximately 0.0046 lumens.