This interactive tutorial explores illumination pathways in the Olympus IX70 research-level inverted tissue culture microscope. The microscope drawing presented above illustrates a cut-away diagram of the Olympus IX70 microscope equipped with lamphouses for both diascopic (tungsten-halogen) and epi-fluorescence (mercury arc) light sources. Also featured is a traditional 35-millimeter camera system (lower front microscope port) and a Peltier-cooled scientific CCD digital camera system attached to an extension tube on the trinocular head. The fluorescence filter cube turret, housed underneath the nosepiece containing a set of objectives, is equipped with up to four unique filter sets mounted in individual cubes.

The tutorial initializes in EPI illumination mode with the Beam Intensity slider set to a value of approximately 75 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 four different filter combinations:

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

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

• Green Excitation (550 nanometers) - Red Emission (620 nanometers)

• Orange Excitation (600 nanometers) - Deep Red Emission (670 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.

Radio buttons also control the optical pathway to the 35-millimeter and CCD cameras systems. By default both the 35mm Camera and CCD Camera checkboxes are marked, and light passes through beamsplitters to both systems. Use the mouse cursor to deselect either camera and remove the appropriate beamsplitter from the optical train.