This study focuses on the design of a lens system operating in the Mid-Wave Infrared (MWIR) range (3.5–4.5 μm) for vascular imaging and blood flow analysis. The MWIR band offers significant advantages, including deeper tissue penetration, reduced scattering, and higher thermal contrast, particularly around body temperature (~37.5°C). These features make MWIR imaging an effective tool for visualizing vascular structures and detecting abnormalities in blood flow. A lens system was designed using ZEMAX and optimized to maximize resolution and contrast for thermal imaging applications. The design exploits the natural thermal emissions of the human body, eliminating the need for external illumination. Results indicate the lens system achieves high sensitivity and resolution, facilitating detailed imaging of small-diameter vessels and thermal anomalies. This innovative approach demonstrates the potential of MWIR-based optical systems for advancing medical imaging technologies, offering a non-invasive, high-contrast solution for cardiovascular diagnostics.