![]() ![]() ![]() The resultant system can capture a single, non-repetitive event at up to 100 billion fps with appreciable sequence depths (up to 350 frames per acquisition). With a collecting objective of an NA = 0.16, the throughput loss caused by DMD’s diffraction is negligible.īy adding a digital micromirror device (DMD) as the spatial encoding module and applying the CUP reconstruction algorithm, we transformed a conventional 1D streak camera to a 2D ultrafast imaging device. Since the DMD’s resolution pixel size (7.2 μm×7.2 μm) is much larger than the light wavelength, the diffraction angle is small (~ 4°). CCD, charge-coupled device DMD, digital micromirror device V, sweeping voltage t, time. ![]() The image reconstruction process follows a strategy similar to CS-based image restoration 15– 19 - iteratively estimating a solution that minimizes an objective function.ĬUP system configuration. This encoded, sheared three-dimensional (3D) x, y, t scene is then measured by a 2D detector array, such as a CCD, with a single snapshot. On the basis of compressed sensing (CS) 14, CUP works by encoding the spatial domain with a pseudo-random binary pattern, followed by a shearing operation in the temporal domain, performed using a streak camera with a fully opened entrance slit. 1), which can provide 2D dynamic imaging using a streak camera without employing any mechanical or optical scanning mechanism with a single exposure. To overcome this limitation, here we present CUP ( Fig. In cases where the physical phenomena are either difficult or impossible to repeat, such as optical rogue waves 13, nuclear explosion, and gravitational collapse in a supernova, this 2D streak imaging method is inapplicable. Although this paradigm is capable of providing a frame rate fast enough to catch photons in motion 11, 12, the event itself must be repetitive-following exactly the same spatiotemporal pattern-while the entrance slit of a streak camera steps across the entire FOV. To achieve 2D imaging, the system thus requires additional mechanical or optical scanning along the orthogonal spatial axis. However, a typical streak camera is a one-dimensional (1D) imaging device-a narrow entrance slit (10 – 50 μm wide) limits the imaging field of view (FOV) to a line. To record events occurring at sub-nanosecond scale, currently the most effective approach is to use a streak camera, i.e., an ultrafast photo-detection system that transforms the temporal profile of a light signal into a spatial profile by shearing photoelectrons perpendicularly to their direction of travel with a time-varying voltage 10. Given CUP’s capability, we expect it to find widespread applications in both fundamental and applied sciences including biomedical research. Using CUP, we visualise four fundamental physical phenomena with single laser shots only: laser pulse reflection, refraction, photon racing in two media, and faster-than-light propagation of non-information. As a result, CUP can image a variety of luminescent-such as fluorescent or bioluminescent-objects. Further, akin to traditional photography, CUP is receive-only-avoiding specialized active illumination required by other single-shot ultrafast imagers 2, 3. Compared with existing ultrafast imaging techniques, CUP has a prominent advantage of measuring an x, y, t ( x, y, spatial coordinates t, time) scene with a single camera snapshot, thereby allowing observation of transient events occurring on a time scale down to tens of picoseconds. Here we demonstrate a two-dimensional (2D) dynamic imaging technique, compressed ultrafast photography (CUP), which can capture non-repetitive time-evolving events at up to 100 billion (10 11) fps. Despite these sensors’ widespread impact, further increasing frame rates using CCD or CMOS is fundamentally limited by their on-chip storage and electronic readout speed 9. In particular, the introduction of electronic imaging sensors, such as the charge-coupled device (CCD) and complementary metal-oxide-semiconductor (CMOS), revolutionized high-speed photography, enabling acquisition rates up to ten million (10 7) fps 8. However, not until the late 20 th century were breakthroughs achieved in demonstrating ultra-high speed imaging (>100 thousand, or 10 5, frames per second (fps)) 7. Capturing transient scenes at a high imaging speed has been pursued by photographers for centuries 1– 4, tracing back to Muybridge’s 1878 recording of a horse in motion 5 and Mach’s 1887 photography of a supersonic bullet 6. ![]()
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