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SWIR in machine vision: how to overcome the invisible challenge
SWIR technology is used in semiconductor inspection, to identify defects that might be invisible under normal light S
hort-wave infrared (SWIR) is a part of the electromagnetic spectrum that lies just beyond the visible range of
light. It typically refers to the wavelength band of light between 900 and 2500nm. SWIR technology has traditionally been
leveraged in more specialised applications due to its ability to see beyond the visible spectrum, offering unique imaging solutions where traditional cameras may fall short. Some applications include semiconductor inspection, to identify defects that might be invisible under normal light; moisture detection in pipes or food production; and inspecting objects under a surface, such as in packaging. More recently, SWIR has been making
its way into the broader machine vision market, driven by advancements in sensor technology, with innovations such as the new Sony SenSWIR sensors, which were designed to provide enhanced image quality, compact designs, and reduced costs. Torsten Wehner, Product Manager at Baumer Group, explains: “In addition to the combination of the visual range up to the SWIR range, the
achievable image quality is significantly better compared to previous InGaAs sensors. This is especially true for the resulting defect pixels and image noise. With the SenSWIR technology, Peltier cooling (TEC) can be avoided in many applications. This makes the cameras significantly cheaper and more compact in design.”
Transitioning to SWIR: The challenges However, transitioning SWIR technology to a broader market comes with its own set of challenges. Companies and organisations using industrial cameras often need to navigate issues related to image quality, camera size, power consumption, and defect pixels. Wehner says: “The challenge for our customers is to understand how image quality can be influenced by which measures in order to achieve the best possible, most stable result in imaging processing. InGaAs technology is not as widespread yet, and the technologies required to manufacture it are different from the familiar silicon- based manufacturing process. Silicon-
22 IMAGING AND MACHINE VISION EUROPE AUGUST/SEPTEMBER 2024
based CMOS technology also took many years to achieve the image quality we know today. The first images from CMOS sensors had very similar characteristics to today’s InGaAs sensors, which are a huge step forward in terms of image quality with SenSWIR technology, but are not yet at the same level as silicon-based CMOS sensors. A key issue is the temperature of the image sensor. The warmer it gets, the more defect pixels appear. Each additional defect pixel can make the subsequent image processing more unstable. Further corrections in the camera will not help.” Baumer has developed several key components to address the issue of defect pixels, focusing on temperature management and advanced correction methods. The design of the camera housing plays a critical role in dissipating heat generated by the electronics, thus reducing the number of defect pixels. Wehner explains, “Our first priority is to create as few defect pixels as possible, which is why we emphasise effective heat dissipation and low power consumption in our camera designs.”
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