Swept coded aperture real-time femtophotography.

Single-shot real-time femtophotography is indispensable for imaging ultrafast dynamics during their times of occurrence. Despite their advantages over conventional multi-shot approaches, existing techniques confront restricted imaging speed or degraded data quality by the deployed optoelectronic devices and face challenges in the application scope and acquisition accuracy. They are also hindered by the limitations in the acquirable information imposed by the sensing models. Here, we overcome these challenges by developing swept coded aperture real-time femtophotography (SCARF). This computational imaging modality enables all-optical ultrafast sweeping of a static coded aperture during the recording of an ultrafast event, bringing full-sequence encoding of up to 156.3 THz to every pixel on a CCD camera. We demonstrate SCARF's single-shot ultrafast imaging ability at tunable frame rates and spatial scales in both reflection and transmission modes. Using SCARF, we image ultrafast absorption in a semiconductor and ultrafast demagnetization of a metal alloy.

Fast wide-field upconversion luminescence lifetime thermometry enabled by single-shot compressed ultrahigh-speed imaging.

Photoluminescence lifetime imaging of upconverting nanoparticles is increasingly featured in recent progress in optical thermometry. Despite remarkable advances in photoluminescent temperature indicators, existing optical instruments lack the ability of wide-field photoluminescence lifetime imaging in real time, thus falling short in dynamic temperature mapping. Here, we report video-rate upconversion temperature sensing in wide field using single-shot photoluminescence lifetime imaging thermometry (SPLIT). Developed from a compressed-sensing ultrahigh-speed imaging paradigm, SPLIT first records wide-field luminescence intensity decay compressively in two views in a single exposure. Then, an algorithm, built upon the plug-and-play alternating direction method of multipliers, is used to reconstruct the video, from which the extracted lifetime distribution is converted to a temperature map. Using the core/shell NaGdF4:Er3+,Yb3+/NaGdF4 upconverting nanoparticles as the lifetime-based temperature indicators, we apply SPLIT in longitudinal wide-field temperature monitoring beneath a thin scattering medium. SPLIT also enables video-rate temperature mapping of a moving biological sample at single-cell resolution.

Single-shot compressed optical-streaking ultra-high-speed photography.

Single-shot ultra-high-speed imaging is of great significance to capture transient phenomena in physics, biology, and chemistry in real time. Existing techniques, however, have a restricted application scope, a low sequence depth, or a limited pixel count. To overcome these limitations, we developed single-shot compressed optical-streaking ultra-high-speed photography (COSUP) with an imaging speed of 1.5 million frames per second, a sequence depth of 500 frames, and an (x,y) pixel count of 0.5 megapixels per frame. COSUP's single-shot ultra-high-speed imaging ability was demonstrated by recording single laser pulses illuminating through transmissive targets and by tracing a fast-moving object. As a universal imaging platform, COSUP is capable of increasing imaging speeds of a wide range of CCD and complementary metal-oxide-semiconductor cameras by four orders of magnitude. We envision COSUP to be applied in widespread applications in biomedicine and materials science.

Fast and high-resolution light field acquisition using defocus modulation.

In the conventional microlens-array-based light field imaging system, there is a trade-off between the angular and spatial resolutions. Light field reconstruction from images captured by focal plane sweeping, such as light field moment imaging (LFMI) and light field reconstruction with back projection (LFBP), can achieve high transverse resolution comparable to the modern camera sensor. However, the acquisition of a series of focal plane sweeping images along the optical axis is time consuming and requires fine alignment. Furthermore, different focal-plane-based light field reconstruction techniques require images with different characteristics. To solve these problems, we present an efficient approach for fast light field acquisition with precise focal plane sweeping capture by defocus modulation, rather than mechanical movement. Also, we verify the validity and the improvement of our system. With the controllable point spread function, we can capture images for light field reconstruction with both LFMI and LFBP. Otherwise, we quantitatively compare the two methods using images captured with the proposed systems.

Light field endoscopy and its parametric description.

In this Letter, we demonstrate the application of light field imaging to endoscopy. By introducing a microlens array into the image plane of a conventional endoscope, the 4D light field can be captured in one snapshot. This information can be used to obtain perspective images and to digitally refocus to different planes. These features allow for the recovery of 3D information in minimally invasive surgery. Important optical setup and performance parameters are derived to enable task specific engineering of the light field imaging system.

Reducing aberration effect of Fourier transform lens by modifying Fourier spectrum of diffractive optical element in beam shaping optical system.

In general, Fourier transform lenses are considered as ideal in the design algorithms of diffractive optical elements (DOEs). However, the inherent aberrations of a real Fourier transform lens disturb the far field pattern. The difference between the generated pattern and the expected design will impact the system performance. Therefore, a method for modifying the Fourier spectrum of DOEs without introducing other optical elements to reduce the aberration effect of the Fourier transform lens is proposed. By applying this method, beam shaping performance is improved markedly for the optical system with a real Fourier transform lens. The experiments carried out with a commercial Fourier transform lens give evidence for this method. The method is capable of reducing the system complexity as well as improving its performance.

Light-field moment microscopy with noise reduction.

We experimentally demonstrate a light-field moment microscopy (LFMM). The proposed technique employs a better estimation of the intensity derivative in solving the Poisson equation and therefore can significantly reduce the noise and error in the reconstructed light-field moment. The light field can be reconstructed then by using the moment, enabling the perspective view and depth estimation of the object. The proposed LFMM can be simply implemented using a standard commercial light microscope. This will open up new possibility for standard microscopes in high-resolution light-field observations.