Personal dimming control, versus a one-size-fits-all lighting system, lets users adjust lighting to suit their personal comfort and the task at hand. This type of personal control in the workplace and other settings has proven physical and psychological benefits, as well as an interrelated impact on occupant satisfaction and productivity. The burgeoning fields of lighting automation, artificial intelligence (AI), and biosensors may all have a role in the next generation of lighting controls that create a responsive environment to enhance comfort, productivity and well-being.

In our work at the University of Southern California’s Human-Building Integration Lab, we are developing a system that can control indoor lighting levels based upon the pupil sizes of occupants in the room. The team’s goal is to create an apparatus, supporting software and controls that can set optimal lighting conditions based on the occupant’s pupil response to lighting conditions. Ultimately, we see benefits in energy efficiency and comfort; improved health outcomes; and increased productivity in office environments and, perhaps, in educational settings.

This interdisciplinary work unites the fields of architecture, medicine and engineering in addressing indoor environmental quality issues. This research is supported by the National Science Foundation and the U.S. Environmental Protection Agency and extends into multiple disciplines of environmental controls, particularly HVAC. Of all the indoor environmental factors, lighting quality is the most significant in relation to occupants’ visual comfort and health, as the body’s reactions to changing lighting conditions are almost instantaneous.

Most existing lighting technologies and research focus on system-centered solutions, which make the users passive participants in the system-control loop. This passiveness could lead to overlighting and other inefficient energy consumption patterns while the building occupants’ environmental comfort and satisfaction are compromised. Today’s LED lighting and digital controls systems are making it easier and cheaper for occupants to proactively participate in controls strategies via personal or direct dimming. And, increasing research concerning the heath impacts of light exposure may reveal additional benefits to personal control.

Bringing personal controls into the realm of direct biometric (hands-off) control has great potential in K–12 schools and healthcare settings, where occupants may be unable to manually operate controls or provide useful feedback on personal comfort levels. The potential for financial benefit in the workplace is tremendous. Improvements in productivity, health and absenteeism could be 100 times any energy saving achieved.

ASL Eye Tracking Glass image
Enter wearables

The goal of this project, entitled "Human-Building Integration: Human-Eye Pupil Size–Based Visual Environmental Comfort Control," is to develop an integrated human-centered intelligent environmental control system that enhances the building occupants’ visual comfort and health. Human pupil sizes constrict or dilate in response to different types of lighting as the environment stimulates the person’s autonomic, parasympathetic nervous system. Even though there is significant diversity in the shapes and sizes of human pupils, we have found that pupil-size-change mechanisms remain consistent among diverse populations.

Therefore, pupil-size changes have great potential to indicate an occupant’s visual sensation and comfort. Given currently available webcam and wearable technologies, pupil-size measurement and pupil-size–driven controls can be easily integrated into current building energy management systems.

Our team has also developed a bio-sensing environmental control protytype device, refining this "wearable" in the lab setting. By adopting an AI algorithm, the control module receives biometric data from the wearable sensor and "learns" the pattern of the user’s pupil sizes as a function of the ambient lighting (i.e., illuminance). It then adjusts the lighting level to maintain a specific pupil size while monitoring any irregular size patterns that are significant.

Beyond the lab setting, the team is currently improving this human-building integration (HBI) lighting control system in a real environment. Over the next year, we’ll be working out implementation issues such as technical practicality, user-friendliness, cost-effectiveness, and privacy protection. These will all come into play as we approach commercialization and improve the system’s overall effectiveness in offices, healthcare environments, and educational facilities, where the lighting affects occupants’ work productivity and health as well as building energy performance.

Image of team's control system.
The team’s control system is shown here as a prototype control module, pupil-size detection procedure, and realtime sensing and control of lighting. Check out some videos here.
Joon-Ho Choi

About Joon-Ho Choi

Joon-Ho Choi, is the associate dean for research and creative work and an associate professor of Building Science in the School of Architecture at the University of Southern California. His primary research interests are in the areas of advanced controls for high-performance buildings, bio-sensing and human-centered environmental controls, smart buildings, and environmental sustainability; as well as comprehensive post-occupancy evaluation, indoor environmental quality and human health, and work productivity.

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