Bench Talk

(Source: Marcin Szczepanski, Michigan Engineering)

Night vision “goggles” were born in the 1930s, at time when military applications were becoming more technological. Not long after, during World War II, they experienced a widespread introduction. While the technology has evolved over the years, the devices remain bulky, expensive, and heavy.

Night vision systems rely on a process to convert near-infrared light into electrons that travel through a vacuum to hit a screen, turning them into visible light. Given that the light is amplified approximately 10,000 times, the user sees clearly in the dark. The downside of the process, however, is that it is power-hungry, creating considerable design hurdles that often contribute to the increased size and cost.

Organic light-emitting diodes (OLEDs) can also convert infrared light into visible light in a one-to-one ratio. Now, however, a new OLED changes that ratio to yield multiple output photons for each input photon. According to researchers at the University of Michigan,^[1] the new OLED approach, when implemented in compact, lightweight glasses, may result in a cheaper device designed for prolonged use.

How it Works

The new OLED solution converts and amplifies near-infrared light into visible light, reaching more than 100 times amplification without using traditional high-voltage components. Remarkably, this light amplification occurs within an ultra-thin film stack—less than a micron (0.001 mm) thick, significantly thinner than a typical hair strand that measures around 50 microns. Since this device operates at a much lower voltage than conventional image intensifiers, it brings reduced power consumption and longer battery life.

By combining a photon-absorbing layer and a five-layer OLED stack, the new OLED converts infrared light into electrons and then into visible light photons. Instead of a one-to-one ratio, however, five photons are produced for each electron passing through the OLED stack. This increases the amount of output light resulting from a given amount of input light.

Although OLEDs were able to convert near-infrared light to visible light previously, there was no net photon gain. The University of Michigan research team, led by Professor Chris Giebink and including postdoctoral researcher Raju Lampande, published their findings in Nature Photonics and demonstrated the first high photon gain in a thin film device.^[2]

Using readily available “off-the-shelf” materials and existing OLED techniques, researchers improved cost-effectiveness and scalability. This paves the way for vital advancements in display tech, upconversion imaging, and neuromorphic optoelectronics.

A Memory Component

This approach is unique because there is a memory effect in the OLEDs that could lead to computer vision systems being able to sense and interpret incoming light signals and images. This effect is known as hysteresis, and broadly speaking, it refers to the dependence of a system’s current state in part on its past inputs. For OLEDs, hysteresis means that the light output at any given moment is influenced by the intensity and duration of previous light exposure, allowing the device to “remember” past illumination and improve current performance based on historical input.

Giebink explained hysteresis, saying that “when illuminating an upconversion OLED, it starts outputting light and when you turn off illumination, it stops outputting light.”^[3] The new device, however, can get stuck “on,” remembering things over time, and this unique memory behavior could create image processing like a human visual system. This feature mimics how neurons in the human brain process information by remembering past signals, which could help OLEDs process and classify images more effectively. With the ability to retain past inputs, these OLEDs are ideal for neuron-like connections that enable them to interpret and classify input images directly, without the need for a separate computing unit to process the data.

Beyond Military and Defense

Traditionally, we associate night vision technology with military and defense applications, but the opportunities for these lightweight OLEDs go beyond that.

In smart cities, this technology could be used to enhance city safety by offering small, portable night vision for police officers and emergency personnel. Additionally, OLED night vision can be linked to IoT networks for smart monitoring in dark spaces. Cities like New York^[4] and Singapore^[5] are already exploring next-gen city programs that could benefit from technology like this.

In autonomous vehicles, OLED night vision sensors provide improved object detection in nighttime conditions, as well as better energy efficiency. This makes them a good option for electric and self-driving cars. The technology could also extend to augmented reality, wearables, and even overlap with various use cases from industrial to wildlife enthusiasts. AR glasses could overlay real-time maps of wildlife for hikers and photographers, while construction employees could leverage these OLEDs to enhance job safety. Furthermore, conservationists could employ tiny machines integrating this technology to watch for nightlife in remote areas. The variety of applications demonstrates just how broad the benefits could be for OLED-based night vision.

The Future of Night Vision

Night vision with OLED technology could be the next leap in how we interact with the world at night. The University of Michigan researchers’ efforts to achieve high photon gain in a compact, thin-film device overcome the limitations of older systems defined by bulkiness, high power consumption, and dependence on complex high-voltage components. Being able to boost light with a fraction of the power footprint means this could be ready for widespread adoption across a range of fields, from defense and surveillance to wearable tech and autonomous vehicles.

This breakthrough was developed through a collaboration with OLEDWorks, a leader in OLED lighting solutions, and RTX, a prominent aerospace and defense innovator, with funding from DARPA.

Sources

[1] https://news.umich.edu/an-oled-for-compact-lightweight-night-vision/
[2] https://www.nature.com/articles/s41566-024-01520-0
[3] https://news.umich.edu/an-oled-for-compact-lightweight-night-vision/
[4]  https://www.nyc.gov/content/oti/pages/press-releases/oti-launches-nyc-smart-city-testbed-program-drones-pilot-lower-greenhouse-buildings-gas-emissions
[5] https://www.smartnation.gov.sg/initiatives/urban-living/