How does a lens ensure high transmittance and low dispersion over a wide spectral range?
Publish Time: 2025-08-26
In modern optical systems, whether used for drone aerial photography, security surveillance, smartphone photography, or precision instrument imaging, lens performance directly determines image clarity, color reproduction, and overall visual presentation. Achieving high transmittance and low dispersion across a wide spectral range is a core quality indicator for lenses. Transmittance affects the amount of light entering and image brightness, while dispersion affects whether artifacts such as purple and green fringing occur along color edges. Optimizing both of these properties requires a systematic and coordinated approach, encompassing material selection, optical design, surface treatment, and manufacturing processes.Achieving high transmittance and low dispersion lies in the precise selection of optical materials. Different glass or resin materials have unique refractive index and Abbe number characteristics, the latter being a key parameter for measuring the material's dispersion. Low-dispersion materials enable light of different wavelengths to travel at closer speeds within the visible and even near-infrared bands, reducing spectral separation caused by differences in refractive index. By utilizing specially formulated low-dispersion optical glass, such as fluorine-containing crown glass or apochromatic materials, lenses significantly suppress blue and red light deviations without sacrificing structural strength, enhancing image sharpness and color purity.Furthermore, the aspherical lens and multi-element design further optimize optical path control. Conventional spherical lenses are prone to spherical aberration and off-axis chromatic aberration at large fields of view or apertures. However, the complex curved profile of an aspherical lens precisely corrects the focusing path of light, converging light incident at different angles onto the same focal plane. Multi-element lens systems, through the optimal combination of positive and negative lens elements, exploit the complementary dispersion properties of different materials to offset chromatic aberration. For example, combining a high-refractive-index positive lens with a low-dispersion negative lens effectively corrects primary and secondary spectral aberrations, improving image consistency across the entire field of view.Surface coating technology plays an indispensable role in improving light transmittance. Untreated lens surfaces can lose significant light due to reflections. Especially in multi-element systems, the accumulated reflections significantly reduce system light throughput. By depositing multiple layers of anti-reflection coating on the lens surface, the principle of optical interference is exploited to cancel out reflected light within specific wavelengths, or even the entire visible range, significantly improving light transmittance. This high-end coating not only covers visible light but also extends into the near-ultraviolet and near-infrared regions, ensuring stable imaging performance even under complex lighting conditions. Furthermore, the coating offers additional features such as hydrophobicity, oil repellency, and scratch resistance, enhancing the lens's environmental adaptability and durability.Manufacturing precision is also crucial. Minor defects such as lens surface error, center thickness deviation, and decentration can affect the accuracy of the optical path and exacerbate chromatic aberration. High-precision molding, precision grinding, and polishing techniques ensure that the geometry of each lens is perfectly consistent with the designed model. Automated inspection equipment, using interferometers and profilometers, thoroughly inspects each lens to ensure stable and reliable optical performance. The assembly of the lens barrel and lens also requires strict control of coaxiality and spacing to prevent mechanical deviations from introducing additional aberrations.Furthermore, the in-depth application of optical design software enables engineers to simulate light propagation across a wide spectrum in a virtual environment, predicting and correcting potential dispersion issues. By optimizing curvature, spacing, and material combinations, they achieve precise control of transmittance and dispersion from the very beginning of the design.In summary, the lens systematically achieves high transmittance and low dispersion across a wide spectral range by selecting low-dispersion optical materials, combining aspheric surfaces with a multi-element achromatic design, applying high-performance multi-layer coatings, and relying on precision manufacturing and testing processes. This comprehensive capability not only enhances image clarity and color fidelity, but also provides a solid foundation for the stable performance of various high-end imaging devices in complex lighting environments.
