Japan Telecommunications Energy Laboratory designs optical sensor nano-level accuracy

Japan Telecommunications Energy Laboratory designs optical sensor nano-level accuracy

Keywords: Sensors, Japan, Telecommunications, Optical sensors

A very small optical positioning sensor has been developed by the Nippon Telegraph and Telephone Corporation's Telecommunications Energy Laboratories(NTT) a sensor with nano-level accuracy.

Formally known as a microencoder, the tiny device has promising applications in precision instruments and in movements, says NTT, to control robot movements.

Combined with a small motor like the ultrasound motors coming into use for the zoom functions in cameras, the microencoder can also be used to determine the position of moving parts by up to ten nanometers, one such being one-billionth of a meter.

The sensor is made from a semi-conductor laser, fluorinated polyamide waveguide that sends the laser light out in two different directions and a photodiode that receives light reflected back from objects and converts that information into electric 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 needed way to determine changes in position. By integrating the semiconductor laser and the photodiode together with the waveguide on the same piece of silicon, the NTT lab was able to design a device that is only about one-tenth the size of conventional microencoders.

The optical positional sensor measures 5mm square when sealed in a resin package to protect core components, and since the microencoder itself measures 1.7 x 2.3mm, the lab aims to "shrink the package to just 3mm square". The goal is to develop a practical device in a year or two, for commercialisation by the NTT Electronics Corp.

Stuart Griffin