Optical filters and lenses are essential components in many aerospace and defense applications. Optical filters are used to manage light by selectively blocking or transmitting specific wavelengths, as well as providing impact resistance, EMI/RFI shielding and improved system performance. In LCD display systems, they are used as cover glass, backlighting, and internal optical components to reduce reflections and enhance visibility. The filters and lenses control specular and diffuse reflection, modify transmitted and reflected color and diffuse light emitted from LEDs used in displays and lighting systems. Optical filters are critical optical components in precision optics applications, including camera, sensor, imaging, lasers, and LiDAR systems.
How Optical Filters Work
Optical filters are constructed using specialized substrates such as borosilicate, soda lime, and chemically strengthened glass, optical polymers, and transparent ceramics.
Additionally, multi-layer coatings are often applied to the substrates to improve filter performance, including spectral range, mechanical durability, impact resistance and ability to withstand harsh environmental conditions.
By selectively absorbing, transmitting, or reflecting certain wavelengths of light, optical filters only allow desired portions of the light spectrum to pass through. One of the most common types are bandpass filters which selectively transmit and reflect certain wavelengths. For instance, longpass filters pass spectral wavelengths above a specific cutoff by isolating a narrow range of wavelengths, and shortpass filters do the opposite.
EMI shielding filters utilize thin film conductive coatings such as Indium Tin Oxide (ITO) and metal alloys to create a uniform low resistance layer with high transmission. By matching the ITO layer refractive index to substrate material and exit medium, optical transmission can be further enhanced. EMI filters absorb and reflect electromagnetic and radio frequencies and are terminated via a perimeter bus bar to create a Faraday cage. Similarly, conductive coatings are used in the fabrication of transparent heaters to ensure low temperature operation of LCD displays and optical systems used in avionic and remote sensing applications.
Coatings and substrates must be carefully selected based on a number of factors, including application, wavelength range, environmental and mechanical durability to ensure reliable system performance.
Applications of Optical Filters
Military and Defense
Optical filters are an essential tool for enhancing the performance of military and defense systems. In Night Vision Systems, filters are used to minimize infrared emissions from displays and lighting, allowing defense teams to have visibility in near-dark conditions.
EMI filters are important to protect electronic displays and electro-optical systems from disruptive electromagnetic interference, as well as, for attenuating radiated emissions from systems.
NIR longpass filters are used in targeting systems to transmit specific frequencies of laser light and in Forward Looking Infrared (FLIR) systems by selectively blocking shorter, interfering wavelengths.
Filters are also used in surveillance, where filters enhance image quality in degraded and contested environments, such as night operations, inclement weather, or high EMI/RFI noise to ensure clear imagery for monitoring and decision-making.
Aerospace
Optical filters are used for several key technologies in the aerospace sector. Filters are used in satellite imaging to enhance imagery, which enables accurate observation for environmental monitoring and reconnaissance. Filters are a critical in avionics; they are used to reduce reflections, electromagnetic interference and to provide Night Vision Imaging System (NVIS) compatibility to provide high clarity and performance of displays and optical systems in the aircraft, ensuring that the systems used provide precise information under unpredictable operational environments.
Cevians’ Precision Optical Filters for Defense and Aerospace
Cevians offers a wide range of optical filters and coatings tailored to meet the rigorous demands of defense and aerospace applications. Our filters are designed to withstand extreme environments, ensuring optimal performance in critical systems. Cevians provides highly customizable solutions, including EMI/RFI filters, transparent heaters, NVIS filters, display cover glass and precision optics to ensure that each filter meets the unique requirements of each demanding application. Our vertically integrated operations include polymer and glass science, NVIS LED production, thin film coating laboratories, machining, fabrication and integration of application specific designs and configurations. Cevians’ high-durability materials and coatings make our optical filters the top choice for mission-critical operations where precision and reliability are essential.
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