| dc.description.abstract | Traditional pyroelectric infrared sensors (PIR sensors) are widely used in smart home and Internet of Things (IoT) applications. However, their sensing range is limited, with a maximum half-angle of approximately 50 degrees, rarely exceeding 60 degrees. This limitation arises due to the effects of the Fresnel phenomenon, vignetting effect, and the cosine fourth-power law, which cause a reduction in light energy and effective optical aperture, thereby constraining sensor performance. This study proposes a reflective prismatic-like structure for large-angle light collection in PIR sensors, addressing sensing blind spots in wide-angle regions. By integrating a multi-focus compound Fresnel lens, the sensing range is significantly enhanced.
The reflective prismatic-like structure converts large-angle incident sensing light signals into small-angle incident light, effectively mitigating the influence of Fresnel losses and vignetting. Unlike conventional designs, it utilizes a total reflection surface, ensuring that light signals undergo at least one reflection, enabling large-angle deflection. This extends the sensing range beyond a half-angle of 60 degrees, and even surpasses 90 degrees. The structure is fabricated using high-density polyethylene (HDPE) as the primary material. Optical behavior is calculated based on Fresnel equations, and universal prismatic-like structural parameters are designed accordingly. Simulations conducted using a custom Python program demonstrate that the optimal design improves the structure’s optical efficiency to over 50%, meeting the minimum energy requirements for pyroelectric elements to detect human bodies.
This study overcomes the limitations of traditional PIR sensors in large-angle light collection, extending the sensing range, reducing blind spots, and enhancing sensitivity. It offers an innovative and efficient solution for smart home and IoT applications. | en_US |