###### Abstract  
This study presents a significant advancement in LED interior lighting through the development and application of Asymmetric Lens-Total Internal Reflection (AL-TIR) optics, with a focus on enhancing lighting uniformity and indoor comfort by simulating sky-like lighting distribution. AL-TIR technology employs asymmetric lenses combined with total internal reflection to efficiently redirect and spread light, achieving a controlled and even ceiling illumination suitable for various interior applications. This research explored the establishment of ideal luminous intensity curves, devised practical AL-TIR optical designs through numerical calculations, and conducted extensive simulations to assess performance in typical indoor environments. Our findings demonstrated substantial improvements in lighting uniformity, with the AL and AL-TIR systems achieving direct illuminance uniformities of 0.78 and 0.83, respectively, compared to traditional tube LEDs at 0.25. These results, validated in several office rooms, highlight the efficacy of AL-TIR optics in revolutionizing indoor lighting design by balancing optimal lighting distribution with occupant comfort and well-being.  
asymmetric lens; total internal reflection; uniform illumination; sky-like ceiling; washing LED luminaire +
Footnote †: journal: Applied sciences  
While alternative solutions like Barrisol stretch ceilings and Philips lightboxes can provide uniform lighting distribution, they are limited by challenges in optical utilization factor (OUF), heat management, and the flexibility to integrate other fixtures or focus on specific areas. These constraints limit the versatility and usability of ceiling space in various lighting scenarios.  
Building on the foundational work by [PERSON] et al. (2013) [11], which detailed intricate freeform optical surface designs, subsequent research has expanded on these technologies. [PERSON] et al. (2016) [12] advanced the field by improving glare reduction in LED streetlights using asymmetric TIR lenses, eliminating the need for luminaire inclining. [PERSON] et al. (2017) [13] and [PERSON] et al. (2018) [14] extended these designs to include off-axis and catadioptric systems for complex road layouts. [PERSON] et al. (2017) [15] and (2019) [16] further optimized LED lighting optics, enhancing light distribution and OUF, and extending these improvements to human-centric applications.  
[PERSON] et al. (2020) [17] discussed designing symmetric and asymmetric freeform lenses for uniform illumination, while [PERSON] et al. (2020) [18] developed lenses for lighting hard-to-reach areas, beneficial in medical and industrial settings. [PERSON] et al. (2020) [19] focused on educational settings, improving blackboard visibility. [PERSON] (2020) [20] improved visibility and OUF by enhancing asymmetric lighting optics for large-area illumination at short distances. [PERSON] et al. (2020) [21] and [PERSON] et al. (2021) [22] explored cost-effective and efficient designs for general and specialized LED applications.  
Our research builds upon these studies by exploring theoretical luminous intensity curves as benchmarks for LED performance, employing asymmetric lens (AL) and total internal reflection (TIR) optics for optimal lighting redistribution. Through comprehensive simulations, we identify linear Asymmetric Lens-Total Internal Reflection (AL-TIR) optics as the optimal form factor for achieving superior ceiling illuminance uniformity. This approach not only mimics natural sky-like conditions but also enhances OUF and versatility, significantly improving indoor lighting quality. While not a comprehensive HCL system, this work contributes to HCL principles by fostering visual comfort and spatial impressions through sky-like, uniform ceiling illumination. By aiming to achieve sky-like, uniform ceiling illumination, this work enhances human-centric lighting quality by fostering visual comfort and spatial impressions that align with natural lighting distribution, supporting human well-being and productivity in interior spaces.