Infrared Thermail Imaging Lenses

Infrared thermal imaging lenses are a type of optical lens that focus infrared light emitted by objects onto an image sensor (chip). The chip then converts the optical signals into electrical signals, ultimately forming a thermal infrared image composed of the thermal infrared differences between the object itself and the background. To minimize the impact of background noise signals, a smaller F-number is preferable. In extremely cold, extremely hot, or highly variable temperature conditions, changes in the curvature, thickness, refractive index, and barrel of the infrared lens can cause the lens to defocus. To ensure clear imaging, the lens needs to be refocused, either manually or electrically. To mitigate the adverse effects of temperature changes, athermal design is required. This typically involves using different optical materials for optical compensation (temperature difference) or designing with mechanical materials that have opposite change trends to the optical materials for opto-mechanical compensation.

The most commonly used material in infrared lenses is germanium crystal with a refractive index of 4.0, suitable for the 2-25µm wavelength range. Silicon crystal with a refractive index of 3.0 is often used for the 1-6µm wavelength range. Due to the limited availability and high cost of raw materials for germanium and silicon infrared crystals, many optical system designs use aspherical or diffractive surfaces to reduce the number of lenses while maintaining excellent imaging performance. With the widespread commercial use of infrared applications such as night vision, gun sights, and automotive systems, chalcogenide glass has become suitable for mass production due to its low raw material cost, high processing efficiency, and good temperature stability.

Infrared thermal imaging lenses are typically divided into two categories based on their wavelength application windows: Mid-Wave Infrared (MWIR) lenses and Long-Wave Infrared (LWIR) lenses.

1. MWIR lenses are suitable for scenes with higher object temperatures. Their operating wavelength mainly falls within the 3.0-5.0µm mid-wave infrared range. They have strong penetration capabilities through smoke and dust, high resolution, and excellent imaging quality. They are usually used with mid-wave cooled detectors, with the aperture located behind the lens. Therefore, the lens and camera are bulky, but they have a long detection range. For example, lenses with focal lengths of 150mm or 300mm can see distances of 10km-30km. They also have good concealment and can operate day and night, making them widely used in military and high-temperature measurement fields.

2. LWIR lenses are suitable for scenes with lower object temperatures. Their operating wavelength mainly falls within the 8.0-14µm long-wave infrared range. They have lower resolution but can provide high-precision temperature measurements. They are usually used with long-wave uncooled detectors. The lens design is commercially driven, with lower costs, lightweight, compact, and easy to maintain. They are widely used in fields such as power, chemical, firefighting, and medical industries.

Bena Optics can process the entire optoelectronic system, including infrared optical lenses (spherical, aspherical lenses using single-point diamond turning technology), system assembly, and full-process debugging services.