There are two types of low-light imaging objective lenses: refractive type and catadioptric-reflection type. The former is suitable for general situations, while the latter is suitable for occasions with a small field of view, a long focal length, and high requirements for light energy.

In addition to requiring high-quality imaging, high transmittance, small geometric distortion, uniform image surface, adjustable luminous flux, and certain optical performance indicators like ordinary photographic objective lenses, special properties should also be considered for low-light photographic objective lenses. :

1) Both large relative aperture and large clear aperture.

2) With automatic aperture mechanism and corresponding circuit.

3) Comprehensively consider the spectral distribution of the night sky, the spectral reflection characteristics of the scene and the spectral response characteristics of the camera tube.

Considering the spectral distribution of the night sky, the objective lens is required to have good transmittance and image quality characteristics in the 04~10um band (especially in the 05~09um range). Optical design eliminates monochromatic aberration with C spectral line (In ₀ = 06563um), and eliminates chromatic aberration with A' spectral line (In ₁ = 0.7682 μm) and D spectral line (In ₂ = 05893 μm) (which also takes into account the low-light camera device The spectral response characteristics of the current low-light camera tube are mainly multi-alkali photocathodes such as S₂₀ and S₂₅).