New high speed DRUM technology puts $100,000 cameras at risk

"Our camera uses a completely new method to achieve high-speed imaging," explained Jinyang Liang, a researcher, professor, and the scientific head of the Laboratory of Applied Computational Imaging at INRS.

"It has an imaging speed and spatial resolution similar to commercial high-speed cameras but uses off-the-shelf components that would likely cost less than a tenth of today’s ultrafast cameras."

The DRUM camera's capabilities are nothing short of impressive and can capture dynamic events at a mind-boggling 4.8 million frames per second in a single exposure.

To demonstrate its prowess, the researchers used it to image femtosecond laser pulses interacting with liquids and laser ablation in biological samples. The innovation promises to impact various fields significantly, including biomedicine and lidar.

The ingenuity behind DRUM.

To comprehend the significance of the DRUM camera, it is essential to delve into the technology that powers it.

Despite the strides made in ultrafast imaging, existing methods remain expensive, complex to implement, and have limitations when it comes to capturing frames and maintaining light throughput or temporal resolution.

To overcome these challenges, the research team devised a novel time-gating method known as time-varying optical diffraction.

In traditional cameras, gates control when light reaches the sensor. The gate is opened and closed rapidly a certain number of times before the image is read, creating a high-speed movie of the scene.

Jinyang Liang realized that manipulating the tilt angle of periodic facets on a diffraction grating, which generates multiple replicas of incident light traveling in different directions, could serve as a way to gate frames at different time points. These frames could then be seamlessly combined to form ultrafast movies.

The key to making this concept a reality was employing a digital micromirror device (DMD) unconventionally. DMDs, commonly found in projectors, can produce the diffraction gate without requiring any mechanical movement, making the system cost-efficient and stable.

Applications and prospects.

In addition to its current capabilities, researchers are actively working on enhancing the DRUM camera’s performance, aiming to increase the imaging speed and sequence depth. They have also set their sights on capturing color information and exploring new applications such as lidar.

"In the long term, I believe that DRUM photography will contribute to advances in biomedicine and automation-enabling technologies such as lidar, where faster imaging would allow more accurate sensing of hazards," said Jinyang Liang.

"DRUM photography may even be applied to nano-surgeries and laser-based cleaning applications," added Xianglei Liu, first author of the paper and formerly of INRS.

Study Abstract:

Single-shot high-speed mapping photography is a powerful tool used for studying fast dynamics in diverse applications. Despite much recent progress, existing methods are still strained by the trade-off between sequence depth and light throughput, errors induced by parallax, limited imaging dimensionality, and the potential damage caused by pulsed illumination. To overcome these limitations, we explore time-varying optical diffraction as a new gating mechanism to obtain ultrahigh imaging speed. Inspired by the pulse front tilt-gated imaging and the space-time duality in optics, we embody the proposed paradigm in the developed diffraction-gated real-time ultrahigh-speed mapping (DRUM) photography. The sweeping optical diffraction envelope generated by the inter-pattern transition of a digital micromirror device enables sequential time-gating at the sub-microsecond level. DRUM photography can capture a transient event in a single exposure at 4.8 million frames per second. We apply it to the investigation of femtosecond laser-induced breakdown in liquid and laser ablation in biological samples.