Lesson 3 - Understanding the Technology Behind Armasight Thermal Imaging Optics

When it comes to thermal and night vision optics, Armasight stands out as a leading company in the field. We have been at the forefront of creating cutting-edge thermal imaging technology for a wide range of applications. We will dive into the complex components that make Armasight's thermal imaging systems so effective. We'll break down the key elements in a way that anyone can understand.

Objective Lens: A Window to the Invisible

At the heart of any thermal imaging system is the objective lens. These lenses are made from unique materials, primarily Germanium or chalcogenide glass, due to their exceptional properties in the infrared spectrum. Germanium is a material you won't find in your daily life, but it's perfect for thermal optics. While our eyes can't see through Germanium, it allows infrared radiation to pass through, especially in the 8-14 um range. This is precisely the range of wavelengths that most thermal cameras use.

In the world of thermal optics, Germanium is the equivalent of glass in regular cameras. Just like how anti-reflective coatings improve visible light camera performance, they can also enhance the performance of IR camera lenses by reducing energy loss and reflections. However, it's worth noting that Germanium can be quite expensive, sometimes even more costly than the thermal imaging core itself.

The specifications of the objective lens play a significant role in the overall performance of a thermal imaging system. The lens's focal length affects magnification and detection range, with longer focal lengths offering better magnification and detection. On the other hand, shorter focal lengths provide a wider field of view, making it easier to spot a target. The F-Stop factor is another essential parameter, where lower F-Stop values transmit more light and energy, improving image quality.

IR Optical Lenses and Elements: The Invisible Spectrum Specialists

Germanium lenses are just one part of the equation. Armasight uses specialized materials like vanadium oxide in their thermal sensors. This material, in the form of microbolometers, are part of the thermal sensor family. These detectors absorb incoming infrared radiation, leading to temperature changes. These temperature changes are then converted into voltage signals, allowing for the creation of thermal images. Unlike photon detectors, microbolometric detectors can operate without cryogenic cooling, which is a significant advantage.

Microbolometer Arrays: Seeing Without Moving

In thermal imaging, microbolometers are arranged in arrays called focal plane arrays (FPA). This array's advantage is its ability to measure the distribution of infrared radiation across a scene without the need for mechanical scanning systems. The microbolometer's structure involves an absorber surface that converts incoming infrared energy into heat, which is measured through changes in resistance. The pixel pitch, defined as the center-to-center distance between microbolometers, is a critical parameter for these detectors. Armasight's ArmaCORE uses a 12-micron vanadium oxide (Vox) microbolometer technology core, ensuring high-quality thermal imaging.

Thermal Sensitivity and Sensor Resolution: Seeing the Unseen Details

Thermal sensitivity, measured as NEDT (noise equivalent differential temperature), is crucial for longwave (LWIR) infrared cameras. It represents the smallest temperature difference that a thermal imaging detector can distinguish. A lower NETD value indicates better thermal contrast, allowing for superior visual acuity.

The sensor's resolution, determined by the number of detector pixels, plays a vital role in a thermal camera's image quality. More pixels mean higher resolution, leading to better image detail and the ability to detect smaller objects from greater distances.

Sensor Frame Rate: Smooth Visuals for Precision

The frame rate is a critical characteristic of a thermal imaging device. A higher frame rate results in smoother video and less lag between the observed scene and the displayed image. A frame rate of 30Hz is typically sufficient for most applications, but recent studies have shown benefits in using frame rates as high as 90Hz for certain tasks, particularly in the field of aviation.

Processing Module/Core: The Brains of the Operation

The signal obtained from the sensor is processed by a dedicated module, responsible for amplification, up scaling, recording, and power distribution. This core, combined with the thermal sensor, is commonly referred to as the "Core."

Display and Eyepiece: Bringing the Image to Life

For displaying thermal images, most systems use micro displays in conjunction with optical eyepieces. These displays can be LCD, FLCOS, or OLED. Armasight's use of AMOLED technology offers several advantages, including true black levels, vivid colors, energy efficiency, and a wider operating temperature range. The display size and resolution also impact the overall system's magnification and image quality.

In conclusion, Armasight's thermal imaging optics rely on a combination of advanced materials, microbolometer technology, sensor sensitivity, and display quality. These components work together to provide users with the ability to see and interpret the invisible world of infrared radiation. Whether for military, hunting, or industrial applications, Armasight's thermal imaging systems continue to push the boundaries of what is possible in the world of thermal optics.