How to Select the Light Source for a Microscope
When purchasing a microscope, how should you select its light source? What aspects should you pay attention to during selection? A wide variety of microscope light sources are available on the market, such as halogen lamps, mercury lamps and LED lamps.
When selecting a light source for a microscope, you need to consider the arc size, namely the size of the luminous area of the light source. For example, a 50 W mercury lamp has an arc size of 110 × 0.13 mm; a 200 W mercury lamp has an arc size of 212 × 0.15 mm; and a 100 W mercury lamp has an arc size of 0.125 × 0.125 mm. It is important to check whether the arc can properly fill the entrance pupil of the optical system for efficient light utilization. For a high-quality microscope, efficient utilization of luminous energy for objectives of all magnifications is a key indicator worthy of attention.
In microscope optical design, light source selection is critical to the overall design. It determines the application scope and cost of the instrument, and also reflects its grade. Research-grade microscopes generally adopt mercury lamps as the primary light source, while simple or dedicated microscopes commonly use halogen lamps.
Another factor to consider is power: whether to choose a high-wattage or low-wattage bulb. In principle, low-wattage light sources are preferred, which benefits structural design and cost control. However, if the wattage is too low, sufficient stable fluorescence excitation cannot be achieved for observation. Whether fluorescence can be excited is related to the light utilization efficiency of the whole imaging system. With reasonable and efficient light utilization, lower wattage can be adopted. It is inadvisable to simply pursue high-power light sources for fluorescence detection, as this will cause fluorophore photobleaching and quenching. Currently supplied epifluorescence microscopes are generally equipped with 100 W mercury lamps, xenon lamps or halogen lamps.
