Light has played a crucial role in human development since the discovery of fire. Over the centuries, humans have continuously innovated and created artificial light sources to illuminate their surroundings. These artificial light sources have not only improved our ability to study and work effectively but have also impacted our physical and mental health. Modern artificial light sources are now designed with a focus on aesthetics, efficiency, and environmental friendliness.
The Evolution of Light Sources
From incandescent lamps to gaslights, discharge lamps, and light-emitting diodes (LEDs), the evolution of artificial light sources has been remarkable. LEDs, in particular, have revolutionized the lighting industry with their high efficiency and eco-friendly features. However, their smaller size compared to traditional light sources necessitates the use of diffusers to spread light effectively over a larger area.
The Importance of Light Diffusers
Conventional light diffusers have been used to direct and spread light in specific directions. These diffusers have periodic surface profiles, periodic refractive index distributions, or light-scattering layers that play a critical role in controlling the diffusion directivity of light. While these diffusers are effective, once fabricated, their properties, including diffusion directivity, cannot be easily changed.
The Breakthrough in Light Diffusion Technology
A recent study conducted by Professor Daisuke Koyama and his team of graduate students at Doshisha University introduces a groundbreaking tunable ultrasonic liquid crystal (LC) light diffuser. This innovative diffuser is based on the generation of non-coaxial resonant flexural vibration, which allows for the control of molecular orientation and refractive-index distribution in the LC layer. Unlike traditional diffusers, the ultrasonic LC diffuser has a thin and simple structure with no mechanical moving parts.
The Working Mechanism of the Ultrasonic LC Diffuser
The ultrasonic LC diffuser consists of a nematic LC layer sandwiched between two glass disks and an ultrasonic piezoelectric transducer. By applying a continuous reverse-phased sinusoidal signal to the transducer, ultrasonic vibration is induced on the glass disks. When the frequency of this vibration aligns with the resonant frequency of the LC diffuser, non-coaxial resonant flexural vibration modes are generated within the LC layer, altering the transmitted light distribution.
One of the key advantages of the ultrasonic LC diffuser is its ability to control diffusion directivity without the need for mechanical components. By changing the electrodes to which the input voltage is applied, the researchers were able to rotate the direction of molecular orientation and, consequently, the diffusion directivity. Additionally, the diffusion angle of the light can be optimized by adjusting the input voltage amplitude, with a maximum diffusion angle observed at 16 V.
The development of the ultrasonic LC light diffuser opens up new possibilities for the lighting industry. By offering a tunable and efficient solution for controlling diffusion directivity, this technology has the potential to enhance the aesthetics and functionality of artificial light sources. As researchers continue to explore the capabilities of ultrasonic LC technology, we can expect further advancements in the field of light diffusion and illumination.