A new ultra-fast image capture device has been developed by scientists at Caltech. | Caltech





A shock wave created by a laser striking slow-moving water has been captured by new ultra-fast photography technology, capturing a billion frames per second. Credit: Caltech

A pulse of laser light travels through a crystal (seen in slow motion), also captured by new ultra-fast photography technology. Credit: Caltech

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RESEARCH ARTICLE |APPLIED SCIENCES AND ENGINEERING

Picosecond-resolution phase-sensitive imaging of transparent objects in a single shot

Taewoo Kim1, Jinyang Liang1, Liren Zhu1 and Lihong V. Wang



Science Advances 17 Jan 2020:

Vol. 6, no. 3, eaay6200

DOI: 10.1126/sciadv.aay6200

Scientists continue to push the limits of current optical devices, especially when it comes to studying physical or chemical phenomena. Recently, a team of Caltech researchers created a new ultra-fast image capture device (pCUP, from the English phase-sensitive compressed ultrafast photography), capable of taking a billion images per second.While this is an absolutely mind-boggling number, this new creation does not set a record. Indeed, some researchers (from the same team) had already developed, in 2018, a camera with a capture frequency of 10 trillion images per second (10,000,000). However, this new device has more than one string to its bow: it can capture transparent objects, as well as other phenomena invisible to the naked eye, such as shock waves for example.While this incredible technology isn't very useful for vacation videos or Instagram selfies, it promises to have a variety of scientific uses across physics, biology, and chemistry.The device works using the innovative technique used in the 2018 model, where light intensity measurements are combined with a static image as well as advanced algorithms.But the device still has a new element, it uses phase contrast microscopy : it is an older photographic technique where changes in the relative positions of light waves, as they pass through different densities , are converted into variations in brightness. This allows transparent objects, such as cells made mainly of water, to be imaged." What we have done is to adapt standard phase contrast microscopy so that it provides very fast imaging, which allows us to image ultrafast phenomena in transparent materials ", explains Lihong Wang, electrical engineer at California Institute of Technology (Caltech).Namely, that phase contrast microscopy was invented by the Dutch physicist Frits Zernike in the 1930s, and exploits the phase changes of a light wave passing through a material. Thus, these speed changes make materials like glass much easier to spot with this technique.As for the latest feature of this new device, the Caltech team calls it lossless encoding compressed ultra-fast technology ( LLE-CUP , from English lossless encoding compressed ultrafast technology). This marks the next generation of cameras and scanners, which capture an entire event at one time, recording the timing of light waves.Wang's previous work added a new component: a charge coupled device. Now, Wang has combined an improved form of this configuration with microscopy that filters out scattered light to map changes that the human eye cannot see. This type of scientific device, more and more sophisticated, will undoubtedly lead to new discoveries on the world which surrounds us, whether it is by taking snapshots of the human body or by recording quantum entanglement.In this case, the scientists managed to capture the movement of a shock wave in water, as well as a laser pulse through a crystalline material. In addition, "this device could be used for many other purposes in the future, because it can be combined with several other existing optical imaging systems," said the researchers.It could for example allow scientists to observe in detail the expansion of the flames in the combustion chambers, or even to record the signals that pass through neurons on a microscopic scale. " When the signals travel through the neurons, there is a tiny dilation of the nerve fibers, which we hope to see. Maybe we could see the communication of a neural network in real time , ”said Wang.