NTT designs optical sensors with nano-level accuracy

Citation

(2001), "NTT designs optical sensors with nano-level accuracy", Sensor Review, Vol. 21 No. 3. https://doi.org/10.1108/sr.2001.08721cab.010

NTT designs optical sensors with nano-level accuracy

NTT designs optical sensors with nano-level accuracyKeywords: Distance, Optical sensors

A very small optical positioning sensor has been developed by the Nippon Telegram and Telephone Corporation's Telecommunications Energy Laboratories. Formally known as a micro encoder, the tiny device has promising applications in precision instruments and in mechanisms to control the movement of robots. Combined with a small motor like the ultrasound motors coming into use for the zoom functions in cameras, the microencoder could be used to measure changes in rotation angle of as little as 0.0002 degrees.

Mounted on a precision instrument, it would be used to determine the position of moving parts by up to ten nanometres (a nanometre is one-billionth of a metre).

The new microencoder is made from a semiconductor laser, fluorinated polyamide waveguides that send the laser out in two different directions, and a photodiode that receives light reflected back from objects and converts that information into electrical signals.

Optical interference occurs when the two laser light beams bounce off an object that is moving in a straight line or rotating, providing the data needed to determine changes in position by integrating the semiconductor laser and the photodiode, together with the wave-guides on the same piece of silicon, the NTT lab was able to design a device that is only about one-tenth the size of a conventional microencoder.

The optical positioning sensor measures 5mm square when sealed in a resin package to protect core components.

Since the microencoder itself measures 1.7 by 2.3mm, the NTT lab aims to shrink the package to 3mm square. The goal is to develop a practical device in a year or two for commercialisation by NTT Electronics Corporation.