Microscope Illumination Lights the Way For Scientific Discovery

Even the most sophisticated of microscopes will not yield high quality images which are genuinely of value to researchers without adequate microscope illumination. The light sources used in microscopy have advanced considerably since the days of van Leeuwenhoek's sightings of "wee animalcules" in the beginning, the only microscope light source available was natural sunlight or after sunset, candlelight.

Naturally, this was not conducive to capturing truly detailed, in depth viewing, but as the optics involved in the design and manufacture of microscopes improved, so did illumination of samples being viewed. From the lowest of low-technology (or no-technology, really in the case of relying on daylight for microscopy) to modern lighting technologies which provide even, glare-free and bright microscope illumination for optimal viewing of samples.

The development of under slide lighting revolutionized microscopy; a simple, yet effective method which forms the basis of almost every modern type of microscope light source in optical instruments. Because of its long useful life, continuous spectrum lighting and low cost, tungsten halogen lamps are the most commonly preferred type of illumination used. These lamps are most often 50 watt or 100 models, depending on the particular instrument that the lamps are being used in.

In strictly optical (as opposed to electron microscopy instruments) microscopes, the light cast by the lamp used as a source of microscope illumination passes through a collector and then a field lens before going through a condenser underneath the stage where it provides the lighting required by the user of the instrument. Virtually every microscope light source for optical instruments from the most rudimentary models for children and casual hobbyists to far more sophisticated instruments designed for use in the clinical or scientific laboratory environment uses roughly this lighting configuration.

Where a brighter light source is desirable, xenon lamps in 75 or 150 watt varieties may be used – these lamps also provide long product life and an even light output across the visual spectrum. These lamps also have the advantage of not requiring a color filter to provide optimal lighting. For even brighter microscope illumination, tin-halide lamps may be used; and for photomicrography and other fluorescence microscopy applications, mercury lamps in 100 watt or 200 watt configurations are the microscope light source of choice. In facilities where semiconductor wafers are manufactured, these powerful light sources are a vital part of the quality control process, providing personnel with the ability to clearly see manufacturing defects in these incredibly small, mission-critical components.

The field of electron microscopy uses yet other varieties of illumination technology. However, in all forms of optical microscopy, whether light-field or dark field microscopy, lamps utilizing one material or another are the means of providing the microscope illumination needed to allow researchers and physicians a clear view of the microscopic world which surrounds us. The concept of a microscope light source has come a long way since the discovery of electrical power, but its purpose remains the same as in the earliest days of microscopy, where scientists had little choice but to (to borrow a phrase) light a candle or curse the darkness.