A Guide to Choosing Lamps

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Light-emitting diodes (LEDs) are rapidly replacing traditional light sources in several industries. However, arc discharge lamps are widely preferred in applications that require specific wavelength ranges. A LED’s monochromatic output can’t match these wavelengths. Lamps have high-intensity emission in the ultraviolet region. Thus, they cover a more extensive wavelength range that current LEDs can’t. The different types of lamps include mercury-xenon (HgXe), xenon flash lamps, deuterium (D2) continuous mode lamps, and xenon (Xe).

Essential Parameters for Selecting a Lamp

When choosing any lamp, one should consider several features, including life expectancy, light intensity, and stability level, all required in the application. Primarily, the wavelength range determines how one chooses a lamp. Some lamps cover a small range, while others cover a more extensive coverage of the electromagnetic spectrum. For instance, mercury-xenon and xenon lamps emit UV to infrared wavelengths, while deuterium lamps only emit ultraviolet wavelengths.

Light intensity is needed whether one needs pulsed or continuous light. The light intensity also determines the input power-the lower the input power, the lower the intensity. However, pulsed lighting such as that in xenon flash lamps is suitable for applications that require a high output power for a shorter duration. 

A lamp’s output stability determines reliability and accuracy. However, certain factors affect the lamp’s stability, including position within the arc, temperature, housing design, and power supply performance. These factors affect the stability of mercury-xenon, deuterium lamp, and xenon. A xenon flash lamp’s stability is affected by several factors, including position within the arc, operating frequency, lamp discharge voltage, and main discharge capacity.

A lamp’s life expectancy affects operating costs and maintenance of the equipment where the lamp has been installed. The longer the lamp’s service life, the lesser the time needed for lamp replacement and the lower the maintenance costs. 

Deuterium Lamps

These lamps contain deuterium gas. They emit UV light, though the lamp’s glass material determines the wavelength range. Again, they only emit in a single direction. Deuterium lamps are used in several applications, including environmental analyzers, spectrometers, and high-performance liquid chromatography (HPLC). These lamps also have better stability than xenon and mercury-xenon lamps.

When using these lamps, one should consider a few things, including the aperture size, power supply performance, and the warm-up period. They also require a stable power supply for the optimal current and ensure that the lamp is at a favorable temperature. The warm-up duration allows the lamp to achieve thermal equilibrium and the aperture size determines the light output intensity. 

Xenon and Mercury-xenon Lamps

These lamps have anode and cathode electrodes in a gas-filled glass bulb. A xenon lamp has high purity xenon gas, and a mercury-xenon lamp has a mixture of mercury and xenon gas. Both lamps release by arc discharge.

Xenon lamps emit a spectrum similar to sunlight, a large spectrum from UV to IR ranging between 185nm to 2000 nm. These lamps have a long life span, high output, and increased stability. They are ideal light sources for various applications, including wafer inspection systems, spectrometers, microscopes, and solar simulators. 

Mercury-xenon lamps emit a spectrum from UV to IR ranging between 185nm to 2000nm. This broad-spectrum has sharp spikes present in the UV. These spikes are also seen in the area parallel to the mercury’s spectral lines. This makes these lamps suitable in applications that need a high intensity in the UV area, such as UV curing. Mercury-xenon lamps have several characteristics, including long service life, high output intensity, and increased stability. These lamps are appropriate for light sources such as UV curing, wafer inspection systems, microscopes, and film thickness measurement systems. 

Whenever using xenon and mercury-xenon lamps, one must consider the cathode erosion, warm-up time, and supply performance. One must leave these lamps on for several minutes to achieve a maximum light output. This is because the bulb has a gas pressure that must achieve equilibrium. 

Xenon and mercury-xenon lamps work on a direct current. Thus, the main and trigger power supplies must be stable to ensure a successful lamp operation. The lamps need a steady optimal current. Again, the cathode requires a favorable temperature. Thus, the main supply should always be stale. When cathode erosion occurs, it affects the lamp’s stability. Therefore, the cathode temperature shouldn’t be too low or too high. 

Xenon Flash Lamps

Xenon flash lamps emit from UV to IR, ranging between 160nm to 2000nm. These compact pulse light sources are used for various applications, including factory automation, medical analysis, biological research, and environmental analysis. These lamps generate less heat; hence they don’t damage any samples. Again, they are ready for use once they are turned on and don’t require a warm-up period. However, their stability is low compared to deuterium, xenon, and mercury-xenon lamps.

One should consider a few items whenever using these lamps. They require a power supply and a trigger socket for operation. Again, they should be shielded to avoid electrical noise. One should also look into the power capacitor. It affects the pulse width and the output intensity. The larger the capacitor, the higher the intensity and more prolonged the flush pulse waveform. These lamps are suitable for several fields, including analytical, medical, and industrial applications. 

Industrial Applications

Lamps are widely used in industrial applications such as UV curing equipment and wafer inspection systems. Xenon and mercury-xenon lamps have a longer life span, high output power, and excellent stability. Thus, they are ideal for wafer inspection systems. Mercury-xenon lamps are suitable for UV curing because inks, adhesives, and coatings use UV light parallel to the mercury’s spectral lines. 

Medical Applications

Lamps are crucial in medical fields because of their use in instruments such as blood analyzers and endoscopes. Xenon lamps have a high output intensity needed for lighting the endoscope. Again, it has a stable light output that allows for the viewing of clear images. Xenon flash lamps and deuterium lamps are the best light sources for blood analyzers. Both have a long life-span and high brightness, and despite the high intensity, these lamps have disadvantages. A deuterium lamp needs at least 30 minutes to warm-up, and a xenon lamp has less stability. 

Various lamps have different characteristics. Hence, they are used in several industries. Though they have their disadvantages, these lamps allow for certain successful applications such as microscopes, UV curing, and solar simulators. One should always consider having the required items before using any lamp.

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