What is the difference between the lens of a thermal imaging night vision device and an ordinary camera lens?

(1) Working band

Thermal imaging night vision device lens: mainly works in the infrared band. Because thermal imaging technology is based on the infrared rays emitted by the detected object to form an image, mid-wave infrared (MWIR, 3 - 5μm) and long-wave infrared (LWIR, 8 - 14μm) are the most commonly used bands for thermal imaging. The lens needs to have good transmittance for these infrared bands to ensure that the infrared rays can be effectively transmitted to the detector.

Ordinary camera lens: works in the visible light band, usually in the range of 380 - 780nm. The optical design and coating of the lens are mainly to achieve the best imaging effect in this visible light range, for example, to enable different colors of light to be accurately focused to obtain colorful and clear images.

(2) Material characteristics

Thermal imaging night vision lens: In order to have good transmittance in the infrared band, special infrared optical materials are often used. Such as germanium (Ge), zinc sulfide (ZnS), zinc selenide (ZnSe), etc. These materials have high transmittance in the infrared region, but may be opaque in the visible light band. Moreover, the physical and chemical properties of these materials are different from those of ordinary optical glass. For example, the refractive index of germanium is higher, and these factors need to be considered in optical design and processing.

Ordinary camera lens: Mainly uses optical glass, such as crown glass, flint glass, etc. These glass materials are carefully selected and formulated to achieve good optical properties in the visible light range, such as low dispersion and high transmittance.

(3) Optical design focus

Thermal imaging night vision lens: The design focus is on the collection and focusing of infrared radiation. Since infrared light has a longer wavelength, its optical properties are different from those of visible light. For example, the diffraction effect of infrared light is more obvious. Therefore, the design of the lens should consider reducing diffraction and improving resolution, while ensuring good collection capabilities for infrared radiation at different angles to improve the sensitivity and accuracy of thermal imaging.

Ordinary camera lenses: pay more attention to color restoration, aberration correction (such as spherical aberration, chromatic aberration, coma, etc.) and distortion control. In order to take high-quality color photos, the lens needs to ensure that visible light of different colors can be focused on the same plane and the image quality is uniform throughout the field of view.

(4) Coating technology

Thermal imaging night vision lens: Coating is mainly used to enhance the transmittance of the infrared band and reduce reflection loss. The coating materials and processes of infrared lenses are different from those of ordinary lenses. For example, a multi-layer dielectric film is used to improve the transmittance of a specific infrared band, and the characteristics of the infrared material and the working environment need to be considered to ensure the stability and durability of the coating.

Ordinary camera lens: In addition to improving the transmittance of visible light, the purpose of coating is also to reduce glare, ghosting and other phenomena, and to ensure accurate color reproduction. By coating the lens surface with different layers of film, such as anti-reflection film, anti-reflection film, etc., the optical performance of the lens in the visible light range can be optimized.

(5) Size and weight

Thermal imaging night vision lens: Due to the characteristics of infrared materials and working requirements, some thermal imaging night vision lenses may be relatively large and heavy. For example, some thermal imaging lenses used for long-distance detection have a large lens diameter in order to collect enough infrared radiation, and the overall weight may also be heavy due to factors such as the density of infrared materials.

Ordinary camera lens: The size and weight vary depending on the lens type (such as wide-angle lens, telephoto lens, etc.) and purpose, but in general there are more miniaturized and lightweight designs to facilitate carrying and installation on various camera bodies to meet the shooting needs of different users.

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