This interactive tutorial explores illumination pathways in the Olympus BX51 research-level upright microscope. The microscope drawing presented above illustrates a cut-away diagram of the Olympus BX51 microscope equipped with a vertical illuminator and lamphouses for both diascopic (tungsten-halogen) and epi-fluorescence (mercury arc) light sources. Also featured is a traditional 35-millimeter camera system, but this could easily be substituted for a Peltier-cooled scientific CCD, digital video, avalanche photodiode, or photomultiplier detector. The fluorescence filter cube turret, housed at the front of the vertical illuminator, is equipped with up to six unique filter sets housed within individual cubes.

The tutorial initializes in EPI illumination mode with the Beam Intensity slider set to a value of approximately 50 percent. An ultraviolet (excitation wavelength of 350 nanometers) interference filter set is positioned in the light path by default. To operate the tutorial, use the Beam Intensity slider to adjust the illumination intensity of either the mercury arc lamp (EPI mode) or the tungsten-halogen lamp (Transmission mode). Under normal circumstances, the intensity of an arc lamp is not variable, however this option has been made available to allow visitors to adjust the intensity of light passing through the microscope optical train in order to compensate for differences in computer monitors used to view the tutorial.

In the EPI illumination mode, the Filter Cube slider can be employed to interchange filter sets in the rotating turret. As mentioned above, the default filter set is an ultraviolet excitation filter with an emission band centered in the blue region of the spectrum (450 nanometers). The currently selected excitation light color and wavelength maximum is presented to the right of the slider. Use the slider to toggle between any one of five different filter combinations:

• Ultraviolet Excitation (350 nanometers) - Blue Emission (450 nanometers)

• Blue Excitation (450 nanometers) - Green Emission (550 nanometers)

• Green Excitation (550 nanometers) - Yellow Emission (580 nanometers)

• Orange Excitation (600 nanometers) - Red Emission (620 nanometers)

• Red Excitation (650 nanometers) - Deep Red Emission (690 nanometers)

A pair of radio buttons located in the lower left-hand corner of the tutorial window can be utilized to toggle between EPI and Transmission illumination modes. When the Transmission mode is selected, the Filter Cube slider is inactivated, although visitors can still use the Beam Intensity slider to control the voltage and intensity of diascopic illumination through the microscope.