Test & measurement T
he electromagnetic spectrum (EMS) ranges from the shortest gamma rays to the longest radio waves, encompassing visible light, ultraviolet (UV), infrared (IR), and more. In modern manufacturing, the ability to precisely measure and generate the optical segment has become essential for a wide array of quality assurance (QA), quality control (QC), and safety applications.
From ensuring the purity of water and food safety to testing battery health of electric vehicles (EVs) and semiconductors wafers for defects, the ability to harness the full potential of the EMS has revolutionised industries and manufacturing processes alike. This feature explores the challenges and opportunities of measuring and generating electromagnetic waves for testing and measurement across several industries, while describing the latest advancements in optical metrology, quantum imaging, and next-generation measurement technologies.
The EMS presents numerous challenges when it comes to measuring and generating electromagnetic waves. These challenges arise from the different physical properties across the spectrum, such as wavelength, intensity, and interaction with materials. Accurate measurement is essential for maintaining consistent product quality, ensuring safety standards are met, and optimising processes in modern factories. The ability to measure light in both the visible and non-visible parts of the spectrum is key for modern quality control. The schematic below shows one example of how the EMS can be utilised to optically measure various gasses. This technique is often used in industrial environments to monitor potential gas leaks.
Traditional sensors to measure light in the visible region of the EMS often use silicon as the semiconductor material. However, silicon’s sensitivity to light only covers the visible region and a small part of the Near Infrared region of the EMS. For certain applications, such as monitoring gas emissions or temperature, alternative parts of the EMS must be used, such as the Near and Mid Infrared.
INVESTIGATING THE NEXT GENERATION OF OPTICAL TECHNOLOGY FOR TEST AND MEASUREMENT
In order to detect these wavelengths, we must use alternative semiconductor material with inherent sensitivity at these wavelengths. Compound semiconductor materials such an Indium Gallium Arsenide (InGaAs) or Indium Arsenide Antimonide (InAsSb) can be used to detect light in these regions. Additionally, the increasing complexity of manufacturing processes makes it difficult to design sensors and measurement systems that can operate across a wide range of frequencies with a high level of precision. As production environments become
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more automated and intricate, there is an ongoing need for precise, reliable, and adaptable measurement tools that can handle this diverse spectrum. Another critical challenge when it comes to measuring electromagnetic waves is the interaction between light and materials. Different wavelengths interact with materials in different ways and it is important to understand these differences to develop techniques that can provide accurate data. For instance, visible light is commonly used for surface inspection and quality control in the semiconductor industry, but IR is employed for temperature measurements and analysis of chemical compositions in various industries. Each of these methods requires different sensor configurations, calibration techniques, and measurement protocols. The evolution of the semiconductor and electronics industries has created a heightened demand for advanced measurement systems that can detect minute imperfections in components. These components often require precise measurements at microscopic scales, making the role of optical metrology even more critical. The integration of these technologies into automated factory environments poses challenges with calibration, system integration, and real-time data analysis. There are
many videos or advertisements of robotic production lines moving in unison and performing balletic choreography to build a car, say.
In the joints of these industrial robots, numerous servo motors are used to accurately control their operations, choreographing precisely the direction, angle and speed of rotation robotic arms. Optical encoders are widely used to deliver this choreography. They help to control these processes, by monitoring these parameters and feeding back this information in real time.
Optical transceiver technology can also be used to transmit commands from the controller to the servo motor. This has the associated benefits of speed of light transmission and immunity to magnetic fields in noisy industrial environments, unlike traditional copper wire data transfer technology. Testing the quality of materials in the automotive industry is complex, as vehicles require extensive safety, performance, and environmental testing. In modern automotive production, X-ray inspection techniques, using technology such as microfocus x-ray sources and x-ray sensors or cameras are used for material inspection in automotive production. In addition, LiDAR (Light Detection And Ranging)
April 2025 Instrumentation Monthly
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