Seeing the light from science
Published on 08 Sep 2021

Dr Grantham K H Pang (Croucher Scholarship 1983, Croucher Fellowship 1986) remembers the first time he used light for communication, when he went on school camping trips in Hong Kong.

“We were taught to use our torches to flash the emergency signal S-O-S,” said Pang, an honorary associate professor at the Department of Electrical and Electronic Engineering (DEEE) at The University of Hong Kong (HKU).

More recently, he has relayed the power of light in modern communications – specifically his specialist interest in Li-Fi wireless technology that uses light to transmit data and position between devices – in presentations to inspire secondary school students with a love of science.

Pang grew up in the Shau Kei Wan area of Hong Kong and attended St Paul’s College before graduating from City University in London and completing his PhD at the University of Cambridge in the UK. He spent 10 years working at the University of Waterloo near Toronto in Ontario, Canada, before returning to Hong Kong in 1996 and accepting a position at HKU.

“St Paul’s is over the road from HKU and every time I see the school, I am grateful to the teachers there for providing the foundation of my education in maths and science,” he said.

Three years ago, Pang volunteered to join the Croucher Foundation’s science communication programme. For his demonstrations to secondary school students during Croucher Science Week, he built a special LED dot matrix display and a small portable receiver. Standing at a distance from the display, he played music on his hand-held receiver, which was transmitted by the LED display.

“This is the first time they would hear music transmitted from a light,” said Pang, whose research interests include LED dot matrix displays, artificial Intelligence, deep learning, fuzzy neural networks, intelligent control, computer vision and image processing, as well as the hot topic of Li-Fi.

“Lighting has changed a lot over recent years and after returning to Hong Kong I became very interested in how to use visible light for communications and not just illumination,” he said.

contactUnlike the camping torches used in his youth, LED lights can switch on and off very quickly. When the switching is over 30 times per second, which is faster than the human eye can detect, the light seems on all the time, he explained. However, with the use of a photodiode, it is possible to detect when the light is on or off and obtain a binary digit zero or one, to form the basis of digital communication.

Many airlines, train and bus terminals use LED dot-matrix displays to provide passengers with up-to-date travel information but with a receiver using a decoding algorithm, the data displays can also be used to broadcast a simultaneous secondary level of digital information. This can be detected and decoded by a mobile phone or other portable device. It is comparable with Bluetooth or radio frequency communications but is directional – the user has to be able to see the light to receive the message.

“I always like to make use of what I have learned or discovered. I hope to be a bridge between the application and the idea. I don’t want all my work to be confined to an academic journal, I would like it to benefit society,” Pang said.

His research has resulted in five US patents filed from Hong Kong, three related to Li-Fi. “Current Li-Fi ideas are derived from my early patents of using visible light as a medium for communications in open space,” he said.

The development of the tri-colour LED dot-matrix display that can broadcast audio information was one of his early patents. The display might be used to display stock prices outside a bank but it can also be embedded with digital data so anyone with a suitable decoder and receiver could receive, say, economic reports and company historical data.

Other practical ideas being developed and derived from Pang’s patents include the use of Li-Fi to transmit directional information to the visually impaired about the location of exits or key facilities, and as a means of underwater communication for divers.

Pang relishes his roles in both research and teaching. “I enjoy all aspects of my job but as I get more mature, I enjoy the teaching much more than I did in my early career,” he said.

That sense of professional satisfaction was enhanced by his participation in the Croucher science communications programme and Science Week, he said. From the training included in the programme he learned how to get his key message across in a manner that is familiar to an audience, realising much of the language he had used in the past was full of jargon and abbreviations.

“I deliberately don’t use the word ‘frequency’ anymore. I just avoid it if I think it does not suit the background of my audience,” said Pang, who also learned not to over-deliver the content but establish a scheme and a suitable pace to deliver a specific message.

“Sometimes I would lose myself in the content of my lectures. I can only apologise to some of the students from my early years in teaching, who must have been lost too,” he said.

Pang is convinced of the need to communicate science to a broader audience. The general public should be aware of the importance of scientific knowledge, and have a basic understanding of science in order to stay abreast of issues ranging from 5G, cryptography and hacking to the spread of COVID-19. A broad understanding of science should be regarded as general knowledge, he said.

He received great satisfaction from seeing students inspired by his presentations in Croucher Science Week, while realising it is too easy for university educators to deliver large quantities of information and knowledge but in the process forget about the audience. “I did not realise I would benefit from the programme but in the end I think I received far more than I contributed,” he said.

Dr Grantham K H Pang obtained his PhD degree from the University of Cambridge in 1986. He worked in the Department of Electrical and Computer Engineering, University of Waterloo, Canada, from 1986 to 1996, when he joined the Department of Electrical and Electronic Engineering at The University of Hong Kong (HKU). Since 1988, he has published more than 212 technical papers and authored or co-authored six books. He has obtained five US Patents for HKU, based on his research work. He has also worked as a consultant and visiting researcher at Hitachi Research Lab, Japan and Mitsubishi Electric Corp. He is a Chartered Electrical Engineer, and a member of the IET, HKIE and IEEE. Dr Pang received his Croucher Scholarship in 1983 and Croucher Fellowship in 1986.