This study investigates how LED light frequency, controlled through pulse width modulation, affects human visual comfort.
The research focuses on identifying the optimal frequency range that minimizes flicker and provides a pleasant viewing experience, which is critical for designing safe and user-friendly LED lighting systems. The authors conducted experiments using different PWM frequencies ranging from 25 Hz to 250 Hz in a controlled intelligent lighting setup, maintaining a fixed illuminance of 300 lux and a color temperature of 6500 K to meet indoor lighting comfort standards. A phototransistor sensor was used to stabilize light levels, and image histogram analysis in MATLAB was applied to measure brightness stability over time.
Experimental results show clear differences in visual comfort across frequency levels. Frequencies at 25 Hz, 50 Hz, and 125 Hz produced significant flicker, leading to large fluctuations in image pixel values and high standard deviations. These variations directly reduced visual comfort and created an unstable lighting environment. In contrast, frequencies around 166 Hz and 250 Hz resulted in nearly constant pixel values and very low standard deviations, meaning no noticeable flicker and consistent illumination.
The study confirms that frequencies at approximately 160 Hz and above effectively eliminate distracting flicker and support better visual comfort. The research also highlights the importance of additional lighting parameters, including color rendering index and color temperature, which work together with frequency to determine overall light quality.
The Kruithof curve was used to verify that the experimental conditions fell within the generally accepted comfortable range for human vision. The histogram method proved to be a reliable tool for quantifying visual stability and assessing comfort levels objectively. In conclusion, the study provides practical guidelines for LED lighting design. To ensure visual comfort and reduce potential eye strain, LED drivers should use PWM frequencies of about 160 Hz or higher. This finding supports the development of healthier, more efficient indoor lighting systems while maintaining energy-saving benefits of LED technology. The combination of appropriate frequency, illuminance, and color metrics creates lighting that is both functional and comfortable for daily use.
