A team of researchers from the Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, has developed a highly efficient method for designing compact mid-wave infrared (MWIR) zoom lenses. The research, published in Sensors, employs the particle swarm optimization (PSO) algorithm to solve complex design challenges associated with high-zoom-ratio lenses. The innovative design offers a zoom ratio of 50× with a compact system that maintains high optical performance, marking an advance in optical engineering. MWIR systems, widely used in applications such as thermal imaging, remote sensing, and surveillance, require lenses that can provide flexible focal length adjustments while maintaining compactness and high-quality performance. Traditionally, designing zoom lenses with high zoom ratios while adhering to spatial constraints has been challenging, especially when optimizing parameters such as system length, magnification, and image quality.
The researchers applied a PSO-based approach to automate the design of zoom lenses, using differential analysis to model the focal length variations under paraxial conditions. By introducing a PSO algorithm, the team was able to efficiently evaluate candidate lens structures, balancing key factors like zoom ratio, lens length, and the field curvature across the zoom range. This method significantly reduces the time and complexity typically associated with the trial-and-error approach used in conventional lens design.
The team’s work begins with an analysis of the zooming process, where the system incorporates three movable lens groups to ensure a compact design while maintaining a high zoom ratio. Unlike conventional systems with two movable lens groups, the addition of a third group allows for more balanced focal power distribution and reduces aberrations, which is crucial for maintaining image clarity across the zoom range.
Using the PSO algorithm, the team was able to optimize the focal powers and the spacing between the lens groups. The final result was a MWIR zoom lens with a focal length range from 20 mm to 1000 mm and a total system length of 530 mm, achieving a zoom ratio of 50×. Notably, the design ensures that the lens can accommodate the high demands of MWIR systems, where compactness and long focal lengths are critical.
One of the key challenges in zoom lens design is the need to balance multiple design criteria simultaneously. The PSO method developed by the researchers evaluates various potential solutions, considering factors such as the zoom ratio, the Petzval field curvature, and the focal length at the telephoto end. The optimization process results in a lens system that not only meets stringent performance specifications but also ensures manufacturability with minimal aberrations.
In practice, the design was tested through simulations and real-time optimization in MATLAB, where 200 particles representing candidate solutions were evaluated over 100 iterations. The results demonstrated a high level of optimization efficiency, with the system achieving an excellent balance of magnification, focal power distribution, and image quality. The final design met the requirement for a compact system with a zoom ratio of 50×, making it suitable for a variety of MWIR applications.
This study made advancements in the fields of thermal imaging and remote sensing. The high-zoom ratio and compact design of the lens make it ideal for use in aerial reconnaissance, surveillance, and other applications where portability and flexibility are essential.
Moreover, the PSO-based method could be applied to other optical systems, enabling more efficient designs in a wide range of technologies that require adjustable focal lengths, such as cameras, telescopes, and medical imaging devices.
While the method has proven effective for MWIR zoom lenses, the researchers suggest that future developments could focus on integrating real-time aberration corrections directly within the PSO framework. Such improvements would further enhance the optimization process, making it even more efficient for larger, more complex optical systems.
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