Liquid-crystal neutral density filter that can be tuned using ultrasound

Area of Science:

• Optics and Photonics
• Materials Science
• Acoustics

Background:

• Conventional neutral density (ND) filters have fixed attenuation levels, requiring manual swapping for different applications.
• Existing variable ND filters often involve complex fabrication and control mechanisms, limiting their practicality.

Purpose of the Study:

• To propose a novel variable ND filter with no mechanical moving parts.
• To enable light exposure adjustment via ultrasonic vibration control of liquid crystal orientation.

Main Methods:

• The proposed filter utilizes glass discs, a twisted-nematic (TN) liquid-crystal (LC) layer, and an ultrasonic transducer.
• An electrical signal induces a resonant flexural vibration, generating acoustic radiation force.
• This force disrupts the LC molecular orientation to control light transmission.

Main Results:

• The ultrasonic vibration effectively controlled the twisted orientation of the TN LC layer.
• Transmitted light intensity was successfully modulated by the input voltage.
• The filter demonstrated a thin and simple structure.

Conclusions:

• The developed ultrasonic variable ND filter offers a mechanical-free solution for light intensity control.
• Its simple design facilitates the development of thinner and more cost-effective optical devices.
• This technology has potential applications in various optical systems requiring adjustable light attenuation.