Seven-Lens Optical Imaging Layout for Low-Light NIR Clarity

The patent employs a hybrid lens system combining plastic and glass materials. Specifically, the third and seventh lenses are made of plastic, while the first, second, fourth, fifth, and sixth lenses are made of glass. This composite material approach enables the system to capture both visible and near-infrared wavelengths effectively, as different materials have complementary transmission properties across these spectral regions, thereby improving low illumination imaging capability without requiring a completely separate optical system for each wavelength range.

The optical imaging system is designed with multi-functional capability to operate across both visible and near-infrared wavelength regions. The lens configuration and material selection enable a single optical system to perform dual spectral functions, capturing images in various lighting conditions including low illumination scenarios where near-infrared detection provides advantage, thus improving reliability without multiplying the entire optical system.

The patent incorporates aspherical surfaces on the third and seventh lenses to optimize light path control within the compact module. The aspherical curvature enables more efficient focusing of light rays across the small aperture, maintaining image quality and reducing aberrations despite the reduced module size. This allows the system to achieve high-resolution imaging in a slim form factor by precisely controlling light propagation through curved surfaces.

The patent employs specific parameter optimizations including the ratio TTL/(2*IMGH) < 3.05 (indicating a compact form factor) and strategic selection of focal lengths and refractive indices for each lens element. These parameter changes enable the miniaturized module to maintain adequate light gathering capability and image quality by optimizing the optical path length, focal ratios, and material properties within the constrained volume.

The patent divides the optical system into seven distinct lens elements with specific refractive powers and material compositions. This segmentation allows each element to contribute to overall resolution while maintaining a compact total length. The first two lenses provide initial light convergence, the third lens (aspherical plastic) corrects aberrations, the fourth lens further focuses light, and the fifth and sixth lenses (cemented together) provide additional refinement, with the seventh lens (aspherical plastic) completing the focusing. This segmented approach achieves high resolution without requiring a single long focal length element.

The patent employs a nested arrangement where the fifth and sixth lenses are cemented together to form an integrated optical element. This nesting reduces the overall device length by eliminating air gaps and mounting structures between these two lenses, while still maintaining their individual optical functions for achieving the desired resolution in a compact form factor.

The patent applies aspherical surfaces selectively only to the third and seventh lenses rather than all lens elements. This local application of complex geometry focuses the aberration correction where most needed in the optical path, while keeping the first, second, fourth, fifth, and sixth lenses as simpler spherical surfaces that are easier to manufacture. This selective approach achieves effective aberration correction without unnecessarily increasing manufacturing difficulty across the entire system.

The aspherical lenses (third and seventh) are made of plastic material, which is generally more amenable to precision molding of complex aspherical surfaces compared to glass. This material selection for specific aspherical elements balances the need for aberration correction with manufacturing feasibility, as plastic injection molding can achieve aspherical precision more cost-effectively than glass grinding and polishing.