Structured illumination and digital lighting at the few-photon level

Lead Research Organisation: University of Strathclyde
Department Name: Inst of Photonics


In recent years, advances in semiconductor based photo-detectors have led to the development of simple and compact detectors that are sufficiently sensitive to detect a single photon incident on the sensing area. These devices had revolutionary impact on instrumentation for the life sciences, and now they are starting to open up new possibilities in optical wireless communications.
At the same time, there have been significant advances in the development of light-emitting diode (LED) based lighting, which is now becoming ubiquitous.

Within the last year, the applicant and his colleagues at the University of Strathclyde have pioneered a new method of optical wireless communications that uses LEDs as transmitters and a semiconductor single photon detector as receiver. Data can be transmitted at extremely low light levels of only 30 photons/bit. Utilising a special encoding scheme, which exploits the statistical distribution of single photon detection events, such a low signal level can be maintained even under the presence of normal ambient background light. This potentially disruptive technology can be scaled to multiple LED transmitters and multiple detectors operating in parallel, opening a vast range of possible applications in imaging, communications, space communications, and robotic control.
The driving vision of the project is to realise such a highly parallel system and link it to specific applications.

During the initial development of this technology it proved crucial to interface the transmitter and receiver with configurable digital electronics to perform digital signal processing (DSP). However, these DSP interfaces do not currently have the capability required for the envisaged parallel system. The applicant and his team will investigate the challenges in integrating essential functionality, such as e.g. clock synchronisation, into the DSP hardware. Their work will enable LED displays with 100 MHz frame rate, enhanced modulation formats, and transmitter interfaces for both active- and passive-matrix LED arrays.

The project involves a broad industrial engagement strategy centred around a close link between the University of Strathclyde and Fraunhofer UK, and capitalising on two recently filed patents. Fraunhofer UK is a knowledge transfer organisation dedicated to facilitating the translation of academic research into commercial development. The University and Fraunhofer are already collaborating on other subjects and the fellowship will enable the candidate to lead the technology transfer activities in this area.
Furthermore the applicant will directly engage with the Advanced Forming Research Centre, the Scottish Centre for Excelence in Satellite Applications, and Aralia Systems, which will help to apply the technology to the specific areas of digitally controlled manufacturing, satellite communications, and surveillance systems.
The applicant will utilise his network of academic and industrial contacts in the UK to extend the application and commercialisation of the technology beyond the above mentioned areas, e.g. to ultra-low power networking units for usage in the internet of things.

Planned Impact

The applicant and his colleagues at the University of Strathclyde pioneered a new research area of high scientific and commercial interest. The fellowship will help the team to maintain their internationally leading role and, crucially, it also ties into a strategy of technology transfer via dedicated knowledge transfer organisations, in particular Fraunhofer UK, and direct collaboration with industry.
The beneficiaries of the research within this project can be categorised into 4 groups:
1.) The worldwide scientific community
2.) UK based knowledge transfer organisations
3.) UK based companies
4.) Technology end users
Each of these groups is discussed in a dedicated section below.

1.) The worldwide scientific community:
The project explores a newly emerged area of research. The opportunities and limitations have so far only been studied in a single, confined scenario (single transmitter, single receiver, on-off keying). The project extends vastly beyond this and thus adds to the scientific knowledge, benefitting researchers worldwide.

2.) UK based knowledge transfer organisations:
Fraunhofer UK, the Scottish Centre for Excellence in Satellite Applications (SoXSA), and the Advanced Forming Research Centre are partners in the project. These organisations will take the mid-TRL technology demonstrators developed in the project into their portfolio for further development towards commercialisation. Notably, the technology is underpinning the creation of a new business centre on digital lighting within Fraunhofer UK.

3.) UK based companies:
Aralia Systems, an SME in the surveillance technologies sector, is partner in the project, and Satellite manufacturer Clyde Space is closely aligned with project partner SoXSA. The research is directly relevant to the products of these two companies and the fellow will actively collaborate with them. IP generated within the project will be available to them via licensing agreements and they can access relevant knowhow through engagement with the applicant and his team.
The technology generated in the project should also be of interest for further UK based companies PureLiFi, PhotonForce, and ST Microelectronics. Collaborative research with these companies will be undertaken as appropriate.

4.) Technology end users:
A huge variety of end users will benefit from the technology through its broad range of applications, including the internet of things (IoT), high speed and low light level imaging, and space communications. The technology has potential for ubiquitous use in IoT-connected low power units (e.g. IoT sensors or autonomous devices), thus having significant societal impact. Similarly, the technology is potentially disruptive for applications in small-satellite communications.
The technology is useful for automated surveillance systems (developed in collaboration with Aralia Systems) and has tremendous prospect for use in future security infrastructure. There is great promise for use of the technology in imaging of delicate light-sensitive samples in life sciences and in cost-efficient high-framerate imaging.
Description This project develops a platform technology based on digitally interfaced light-emitting diodes and silicon single photon detectors. There haven been findings both in the underlying technology development and in the application of this technology in certain areas.
Technology development:
- A new device generation of high-density LED transmitters with high speed digital addressing has been developed
- A chip-scale transceiver has been developed that employs special encoding to operate and synchronise at low optical powers (few photons per bit)
- It has been shown that LED transmitters made by a new fabrication process - so-called transfer printing - have excellent properties for structured light applications
Application-specific findings:
- We have mapped out the performance envelope of LED/single photon detector optical links for use in inter-satellite communications
- Digital structured illumination with LEDs has been applied to 3D imaging
- Digital structured illumination with LEDs has been applied to optical camera communications
Exploitation Route This award creates a platform technology that can form an important part of the portfolio of the Fraunhofer Centre for Applied Photonics, and that can be adapted to a range of specific applications.
Sectors Aerospace, Defence and Marine,Digital/Communication/Information Technologies (including Software),Electronics,Manufacturing, including Industrial Biotechology

Description We are aware that our research has influenced the activities of our industrial partner Aralia Systems. They are actively investigating routes of translating our findings to their products, Since this project only started a few months ago and we have been collaborating with Aralia in previous projects, only a small part of this impact can be attributed to this project at the moment.
First Year Of Impact 2018
Sector Aerospace, Defence and Marine
Impact Types Economic

Title Angular alignment monitoring using structured illumination from an LED array 
Description A 16x16 light-emitting diode (LED) array has been used to monitor the angular alignment between the array and a remote single photon avalanche diode (SPAD) detector. For this purpose, a lens was used to project the LED array such that each LED element corresponded to a 1.8 degree x 1.8 degree solid angle. The SPAD was placed in the projection cone at a distance of approximately 2.5 m. The LEDs were modulated using on-off-keying at 2 kb/s super-imposed with a 25 MHz, 25% duty cycle square wave. Data were sent using 38 bit long frames, where the first 6 bits were a fixed sequence "001101", used for clock synchronisation, and the remaining 32 bits were the payload. The payload bits were chosen such that each individual LED transmitted a unique digital fingerprint. The SPAD receiver could then identify the received fingerprint and thus determine which solid angle (with respect to the LED array) it was located in. The angular alignment was then deliberately changed to demonstrate live tracking of the alignment. This dataset contains the live tracking result as well as a record of the phase difference between transmitter and receiver clocks that demonstrates the clock synchronisation using the preamble of the data frames. clock_phase.txt: First column: frame number Second column: phase difference between transmitter and receiver clocks in degrees row_count.txt: First column: time in seconds Columns 2-17: These correspond to rows 1-16 of the LED array. For each 0.25 seconds time bin starting at the time specified in the first column of this file, the numbers in these columns indicate how often the recorded position was in the corresponding LED row. column_count.txt: First column: time in seconds Columns 2-17: These correspond to columns 1-16 of the LED array. For each 0.25 seconds time bin starting at the time specified in the first column of this file, the numbers in these columns indicate how often the recorded position was in the corresponding LED column. 
Type Of Material Database/Collection of data 
Year Produced 2019 
Provided To Others? Yes  
Description Collaboration with Aralia Systems on digital lighting 
Organisation Aralia Systems Ltd
Country United Kingdom 
Sector Private 
PI Contribution - development of device technology for digitally modulated lighting - development modulation formats to be used in digitally modulated lighting
Collaborator Contribution - provision of image processing software - provision of application-specific know-how
Impact This collaboration has been ongoing for several years and was supported by different grants in the past. No reportable outcomes specifically under grant EP/S001751/1 yet. This collaboration is multidisciplinary and spans the fields of Applied Physics, Electrical Engineering, and Machine Vision.
Start Year 2018
Description Collaboration with Fraunhofer UK on Digital Lighting 
Organisation Fraunhofer Society
Department Fraunhofer Centre for Applied Photonics (CAP)
Country United Kingdom 
Sector Academic/University 
PI Contribution - low to mid TRL technology development in areas of strategic interest for the partner - Education of highly skilled workforce - opportunities for mutually leveraged funding
Collaborator Contribution - Co-funding of a PhD student - Access to facilities - provision of a route to impact for our research through a dedicated bridging-the-gap initiative - opportunities for mutually leveraged funding
Impact A co-funded PhD student position has been filled, due to start in October. The collaboration is not multi-disciplinary at the core, although it is likely to seed multidisciplinary engagements with third parties.
Start Year 2018
Description Quantum City at the Royal Institution 2019 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Schools
Results and Impact A technology demonstrator was showcased at the Royal Institution in London at an event targeting the general public and in particular school children. This was designed as an outreach event to communicate research on quantum technologies to a wide audience. Several visitors expressed being intrigued by the technology they saw.
As part of this event, video footage of each demonstrator was taken and subsequently made public via youtube.
Year(s) Of Engagement Activity 2019
Description Quantum Showcase 2018 and 2019 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact Attendance as exhibitor at the Quantum Showcases 2018 and 2019 in London.
The events were each attended by several hundred people, comprising company delegates, academics, knowledge transfer organisations, politicians, and others with related interest.
Several 10s of the delegates engaged in detailed discussions about our research.
Year(s) Of Engagement Activity 2018,2019
Description Robotics and Artificial Intelligence Showcase 2019 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact A technology demonstrator was showcased at this event to engage with the robotics community. The stand was shared with our colleagues from Fraunhofer UK. The event raised awareness of our technology among UK robotics industry and researchers.
Year(s) Of Engagement Activity 2019