Kobe devises one-pixel camera for recording holographic movies

22 May 2025

New technique can obtain images outside the visible spectrum and even through tissues.

A new camera arrangement developed at Kobe University, Japan, can record three-dimensional movies with a single pixel. The technique also obtains images outside the visible spectrum and even through tissues. The Kobe team led by Yoneda Naru says that the development “thus opens the door to holographic video microscopy”.

Holograms have scientific applications in both sensors and in microscopy. Traditionally, holograms require a laser for recording, but more recently, techniques that can record holograms with ambient light or light emanating from a sample have been developed.

There are two main techniques that can achieve this: one is called “FINCH” and uses a 2D image sensor that is fast enough to record movies, but is limited to visible light and an unobstructed view, while the other is called “OSH,” which uses a one-pixel sensor and can record through scattering media and with light outside the visual spectrum, but can only practically record images of motionless objects.

Kobe University applied optics researcher Yoneda wanted to create a holographic recording technique that combines what he calls “the best of both worlds”. To tackle the speed-limiting weak point of OSH, he and his team constructed a setup that uses a high-speed “digital micromirror device” to project onto the object the patterns that are required for recording the hologram.

‘Bullet train speed’

“This device operates at 22 kilohertz, whereas previously used devices have a refresh rate of 60 hertz. This is a speed difference that is equivalent to the difference between an old person taking a relaxed stroll and a Japanese bullet train,” said Yoneda.

The Kobe team have described the achievement and the results of their proof-of-concept experiments in a paper in Optics Express. They show that their setup can not only record 3D images of moving objects, but they could also construct a microscope that can record a holographic movie through a light-scattering object — a mouse skull in this case.

The team concedes that the current frame rate of just over one frame per second “is still fairly low”. But Yoneda said that they have showed in calculations that they could in theory push that frame rate up to 30 Hz, which is a standard screen frame rate. This would be achieved through a compression technique called “sparse sampling,” which works by not recording every portion of the picture all the time.

So, where will such holograms be usefully deployed? Yoneda explained, “We expect this to be applied to minimally invasive, three-dimensional biological observation, because it can visualize objects moving behind a scattering medium. But there are still obstacles to overcome.

“We need to increase the number of sampling points, and also the image quality. For that, we are now trying to optimize the patterns we project onto the samples and to use deep-learning algorithms for transforming the raw data into an image,” he added.