NTT designs optical sensor with nano-level accuracy

Citation

(2002), "NTT designs optical sensor with nano-level accuracy", Sensor Review, Vol. 22 No. 3. https://doi.org/10.1108/sr.2002.08722cab.005

NTT designs optical sensor with nano-level accuracy

NTT designs optical sensor with nano-level accuracyKeywords: Distance measurement, Encoder

An extremely small optical positioning sensor has been developed by Japan's Nippon Telegraph & Telephone Corporation, by its Telecommunications Energy Laboratories. Formally known as a microencoder, 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 function in cameras, the microencoder can also be employed for measurement of changes in rotation angle of as little as 0.002°.

Mounted on a precise instrument, it can be used to determine the position of moving parts by up to 10 nanometres. A nanometre is one-billionth of a metre. The new microencoder is made from a semiconductor laser, flourinated polyamide waveguides that send the laser light 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 waveguides 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 positioning sensor measures 5mm square when sealed in a resin package so as to protect core components. Since the microencoder itself measures 1.7 x 2.3mm, the NTT lab technicians aim to develop a practical device during 2002 or 2003 for commercialisation by NTT Electronics Corp.