They do it with mirrors

2019-03-07 11:07:02

By Peter Hadfield in Tokyo MIRROR balls—think John Travolta—have inspired an idea for improving the way computers communicate over a wireless office network. Local networks that use infrared beams run into problems when people walk into the beam and cut the link—a big problem in crowded offices. Channel-surfing couch potatoes have a similar problem when someone gets in the way of their TV remote control. The frustration could soon be over thanks to a device called a chaos mirror, invented at the Advanced Telecommunications Research Institute (ATR) in Kyoto, Japan. This distant cousin of the mirror ball splits a narrow incoming beam into a widely spread array of reflected beams, vastly increasing the chances of the beam finding the intended receiver. Some infrared networks already use simple mirrors on the ceiling to reflect infrared network signals, but a single reflected beam may still miss its target. Others use specular reflection off the rough surface of the ceiling, but this absorbs energy and weakens the beam. The chaos mirror is different. It consists of a box enclosing seven highly reflective surfaces: three flat and four curved. As an infrared beam bounces around inside the box, it is split into many separate beams that emerge at a variety of angles. Researchers at ATR say that 80 per cent of the beams entering the box are reflected no more than 20 times and that 88 per cent of the incident energy is reflected. The performance of the chaos mirror is further improved by moving the incident beam in a narrow arc, so that its extended reflections cover an even wider area. Researchers say that by moving the beam in a 0.2-degree arc, a 50-centimetre-wide chaos mirror can achieve complete coverage of an office. ATR’s development comes as infrared networking systems are growing in capability. The computer industry’s Infrared Data Association (IrDA) is considering boosting the speed of infrared wireless networking systems to 16 megabits per second—four times the current speed possible for computer-to-computer infrared data transfers. But even these new 16-megabit-per-second systems will only be able to connect to computers—or peripherals such as printers—that are 1 metre away or less, at an angle of no more than 15° from the infrared transmitter. IrDA’s plan is to increase both the range and degree of coverage possible: one plan calls for reception equipment to be boosted to 180° coverage at a 10-metre range. It is in such wide-angle systems that the chaos mirror is most likely to be used. “But there are a number of other applications for this technology,” says Peter Davis, a senior researcher on the ATR laboratory team that developed the mirror. Industrial robots often need to scan an object with a laser beam in order to analyse what is in front of it—but currently they need motors to move the scanning mirrors that move the beam. “One chaos mirror could replace these,