Extremely-high Speed Inversion Imaging Based On Light-field

As a kind of instrument for capturing the optical transients, high-speed imaging technology extremely extends the time resolving power of human eyes. The high-speed imaging technology plays a great role in the research field of nuclear physics, laser fusion, blast physics, lattice vibration, biological reaction process, etc. Although the temporal resolution of the existing high-speed technology can be picosecond, even femtosecond, the imaging systems with complicated structure and poor anti-jamming capability can only be implemented in the laboratory.Fisrt, this paper introduces the development of high-speed imaging technology, domestic and foreign research status. Additionally, the principle of light field imaging and definition of time-varying light field are introduced detailedly. Then we propose an extremely-high speed inversion imaging based on light-field. The novel extremely high-speed thchnology combines the light-field technology, high-speed imaging technology and computational imaging technology. Utilizing the additional information in time-varying light-field data and version algorithm, high-speed imaging can be carried out in single snapshot. Compareing with the existing technology, this high-speed imaging system whose frame intervals can be adjusted flexibly is easy to operate, simply and reliably. In addition, it can be used as high-speed stereoscopic imaging equipment.The light field date of free space contains the 3-diamentional spatial information, and the extra time information is contained in time-varying light field data. It means that the spatio-temporal information can be extracted by converting the time-varying spatial axis to the time axis. First, the time-varying light field is captured by a special imaging system with a microlens array between the main lens and sensor. Each microlens can be considered as a macro-pixel, and the sensor pixels behind each microlens are considered as subpixels. Then the time information of the light field can be extracted through the computational imaging technology. Last, the high-speed imaging can be carried out by inverting the independent transient information in temporal sequence. In mathematical calculation, a linear decreasing of the subpixel number or microlens size results in a linear improvement of the temporal resolution. Specially, better temporal resolution can be achieved by decreasing the pixel size. Our simulation results show that there is an optimized subpixel number for the optimized temporal resolution, and more or fewer subpixels will both lead to lower temporal resolution.In simulation, we use the optic software ZEMAX to image the reflection and refraction of a sigle laser pulse. The framing rate of this system can be up to 1×1011 fps with high pixel resolution(451×451). With the better sensor, lens and inversion algorithm, the better framing rate and pixel resolution can be carried out.Lastly, we put forward the conception and scheme of experiment, summarize the content of this article, and make a prospect for the future researches.