Technology insights

Tungsten light bulbs – the broadband standard

The tungsten (halogen) lamp is commonly used as a light source for absorption spectroscopy in the near-infrared wavelength range due to its broad radiation spectrum (Fig. 1). It is also employed in high-volume gas sensing applications, such as measuring CO₂ and hydrocarbons. However, the fragile and thin wire filament does not meet all the requirements of an ideal light source. To ensure reliable and highly accurate measurements, a stable and reproducible filament position is crucial. Achieving this stability involves complex and high-precision manufacturing of light bulbs. Shocks and vibrations might also cause the lamp intensity to flicker and limit the accuracy of measurements. In practical applications, time-consuming effort is often required to position the incandescent lamp correctly.

Improving the filament

The photometric properties of the filament are largely determined by its geometry. The preferred light source is a flat filament with a square light-emitting surface. Most of the emitted light radiates perpendicularly from the flat surface of the filament, aligning with the collection optics for maximum efficiency. INFRASOLID’s unique emitter technology provides free-standing metal-sheet filaments made of a monolithic high-melting metal by emitting a broad spectrum of light in the near- and mid-infrared range (Fig. 2). Unlike the tungsten wire filament that can move in all spatial directions during vibration and shock, the metal-sheet filament experiences only very limited movement along one axis, similar to a clamped sheet of paper. This provides higher mechanical and optical stability, enabling more accurate measurements in harsh environments and with hand-held devices. It also eliminates the need for time-consuming lamp positioning.

Customization

Metal-sheet filaments can be manufactured in different sizes and geometries to easily adapt to customer-specific applications. The larger area of the metal-sheet filament results in higher optical output (see Fig. 1). As the availability of broadband emitting LEDs in the near- and mid-infrared spectral range is very limited thermal emitters like the light bulb will continue to be the standard light source for absorption spectroscopic applications.

SMD-packaged infrared emitters

SMD stands for Surface Mount Device and refers to electronic components that are mounted directly onto the surface of printed circuit boards (PCBs). These packages are designed to be smaller and more efficient than traditional through-hole packages, which are still the standard of infrared (IR) optical components. However, SMD packages are the dominant choice in modern electronics manufacturing due to their advantages in size, cost, performance, and ease of automation in assembly.

INFRASOLID’s unique and patented infrared emitter technology allows the fabrication of highly efficient and miniaturized thermal IR emitters in different SMD packages. As shown in Fig. 1, the high degree of miniaturization enables a compact arrangement of IR emitter matrices with individually controllable elements. The SMD-packaged IR emitters feature a broadband radiation spectrum and can be equipped with different filter windows allowing to emit different wavelengths, i.e. to display different colors.

Automation and high-volume applications

SMD technology increases the efficiency and automation of PCB assembly, leading to higher production rates, fewer errors, less waste, and reduced costs. SMD components tend to be more robust to physical shock and vibration because of their small size and larger surface area in contact with the PCB. The small size enables a higher density of components on a PCB, leading to smaller, more compact electronic devices. SMD-packaged infrared emitters will therefore pave the way to completely new applications, like in hand-held, portable, and wireless devices for gas sensing, material analysis, and remote sensing.

Remote sensing applications

A SMD IR emitter array, e.g. with 3x3 elements, can generate different IR characters, as shown in Fig. 2, for the communication and identification in remote sensing applications as well as for precise alignment of optical systems. It enables also a detection in challenging visual conditions, harsh environments, and over long-distances.

Let's roll the infrared dice together and ask for our SMD IR emitters in your future applications!