An Improved Microscope Lamp.

The new inclined binocular microscopes when used with high-power objectives require much light to illuminate adequately the field of view. At least three times the light is necessary as for a similar optical combination on a monocular instrument. The ordinary opal bulbs even when over-run do not provide sufficient illumination, and of course with them there is no possibility of employing a light filter when using the highest powers. There is on the market a number of high-intensity lamps using a 6-volt 5-amp. or 8-volt 6-amp. short spiral filament bulb. These have several disadvantages. The light source is so small that when using the Kohler system of illumination the back lens of the objective will not be filled unless there is a short focus lens condenser, which means that its effective diameter is small. Moreover, these lamps are small, the concentration has to be accurate, and, as the bulb has to be run almost at its full capacity, the lamphouse gets very hot. When a new bulb has to be used the centration must again be adjusted, and it may take some time to set up the whole lamp before the best working conditions are obtained. Also, on the existing lamps the filter holder is not convenient, particularly when rapid changes from one filter to another are required. These disadvantages are overcome in the design to be described.