Although fixing the blurring caused by the motion of independent objects still remains challenging, single-photon imaging is the future of high-speed digital photography and vastly surpasses conventional cameras in low-light conditions. Recently, researchers at Tokyo University of Science developed an innovative deblurring approach that accurately estimates the motion of individual objects and adjusts the final image accordingly with a strategy to produce high-quality images even in complex dynamic scenes and may find applications in medicine, science, and security.
These days, many state-of-the-art cameras for demanding applications rely on mechanisms that are considerably different from those in consumer-oriented devices. One of these cameras employs what is known as “single-photon imaging,” which can produce vastly superior results in dark conditions and fast dynamic scenes.
This type of imaging has few ways to deal with moving objects; the movement of the object has to be much slower than the exposure time to avoid blurring, which occurs when taking pictures with regular CMOS cameras, like the ones on smartphones. Single-photon cameras capture a rapid burst of consecutive frames with very short individual exposure times. These frames are binary―a grid of 1s and 0s that respectively indicate whether one photon arrived at each pixel or not during exposure. To reconstruct an actual picture from these binary frames (or bit planes), many of them have to be processed into a single non-binary image. This can be achieved by assigning different levels of brightness to all the pixels in the grid, depending on how many of the bit planes had a “1” for each pixel.
The completely digital nature of single-photon imaging allows for designing clever image reconstruction algorithms that can make up for technical limitations or difficult scenarios. At Tokyo University of Science, Japan, Professor Takayuki Hamamoto has been leading a research team focused on taking the capabilities of single-photon imaging further. In the latest study by Prof. Hamamoto and his team, which was published in IEEE Access, they developed a highly effective algorithm to fix the blurring caused by motion in the imaged objects, as well as common blurring of the entire image such as that caused by the shaking of the camera.
A motion estimation algorithm tracks the movement of individual pixels through statistical evaluations on how bit values change over time (over different bit planes). In this way, as demonstrated experimentally by the researchers, the motion of individual objects can be accurately estimated. Prof. Hamamoto remarks:
Our tests show that the proposed motion estimation technique produced results with errors of less than one pixel, even in dark conditions with few incident photons
The team developed a second algorithm that pixels with a similar motion, thereby identifying in each bit plane separate objects moving at different speeds, which allows for deblurring each region of the image independently according to the motions of objects that pass through it. Prof. Hamamoto adds:
Methods for obtaining crisp images in photon-limited situations would be useful in several fields, including medicine, security, and science. Our approach will hopefully lead to new technology for high-quality imaging in dark environments, like outer space, and super-slow recording that will far exceed the capabilities of today’s fastest cameras
He also states that even consumer-level cameras might timely benefit from progress in single-photon imaging.