Fringe optimization for structured illumination super-resolution microscope with digital micromirror device

Structured illumination microscopy(SIM)is a promising super-resolution technique for imaging subcellular structures and dynamics due to its compatibility with most commonly usedffuorescent labeling methods.Structured illumination can be obtained by either laser interference or projection of fringe patterns.Here,we proposed a fringe projector composed of a compact multiwavelength LEDs module and a digital micromirror device(DMD)which can be directly attached to most commercial invertedffuorescent microscopes and update it into a SIM system.The effects of the period and duty cycle of fringe patterns on the modulation depth of the structured lightfield were studied.With the optimized fringe pattern,1:6×resolution improvement could be obtained with high-end oil objectives.Multicolor imaging and dynamics of subcellular organelles in live cells were also demonstrated.Our method provides a low-cost solution for SIM setup to expand its wide range of applications to most research labs in thefield of life science and medicine.

Superpixel-Based Complex Field Modulation Using a Digital Micromirror Device for Focusing Light through Scattering Media

We present a digital micromirror device（DMD） based superpixel method for focusing light through scattering media by modulating the complex field of incident light. Firstly, we numerically and experimentally investigate focusing light through a scattering sample using the superpixel methods with different target complex fields.Then, single-point and multiple-point focusing experiments are performed using this superpixel-based complex modulation method. In our experiment, up to 71.5% relative enhancement is realized. The use of the DMDbased superpixel method for the control of the complex field of incident light opens an avenue to improve the enhancement of focusing light through scattering media.

Arbitrary amplitude femtosecond pulse shaping via a digital micromirror device

An ultrafast spectrum programmable femtosecond laser may enhance the performance of a wide variety of scientific applications,e.g.,multi-photon imaging.In this paper,we report a digital micromirror device(DMD)-based ultrafast pulse shaper,i.e.,DUPS,for femtosecond laser arbitrary amplitude shaping-the first time a programmable binary device reported to shape the amplitudes of ultrafast pulses spectrum at up to 32 kHz rate over a broad wavelength range.The DUPS is highly effcient,compact,and low cost based on the use of a DMD in combination with a transmission grating.Spatial and temporal dispersion introduced by the DUPS is compensated by a quasi-4-f setup and a grating pair,respectively.Femtosecond pulses with arbitrary spectrum shapes,including rectangular,sawtooth,triangular,double-pulse,and exponential profile,have been demonstrated in our experiments.A feedback operation process is implemented in the DUPS to ensure a robust and repeatable shaping process.The total effciency of the DUPS for amplitude shaping is measured to be 27%.

High-speed playback of spatiotemporal division multiplexing holographic 3D video stored in a solid-state drive using a digital micromirror device

We propose a high-speed playback method for the spatiotemporal division multiplexing electroholographic three-dimensional(3D)video stored in a solid-state drive(SSD)using a digital micromirror device.The spatiotemporal division multiplexing electroholography prevents deterioration in the reconstructed 3D video from a 3D object comprising many object points.In the proposed method,the stored data is remarkably reduced using the packing technique,and the computer-generated holograms are played back at high speed.Consequently,we successfully reconstructed a clear 3D video of a 3D object comprising approximately 1,100,000 points at 60 frames per second by reducing the reading time of the stored data from an SSD.

Estimation-free spatial-domain image reconstruction of structured illumination microscopy

Structured illumination microscopy(SIM)achieves super-resolution(SR)by modulating the high-frequency information of the sample into the passband of the optical system and subsequent image reconstruction.The traditional Wiener-filtering-based reconstruction algorithm operates in the Fourier domain,it requires prior knowledge of the sinusoidal illumination patterns which makes the time-consuming procedure of parameter estimation to raw datasets necessary,besides,the parameter estimation is sensitive to noise or aberration-induced pattern distortion which leads to reconstruction artifacts.Here,we propose a spatial-domain image reconstruction method that does not require parameter estimation but calculates patterns from raw datasets,and a reconstructed image can be obtained just by calculating the spatial covariance of differential calculated patterns and differential filtered datasets(the notch filtering operation is performed to the raw datasets for attenuating and compensating the optical transfer function(OTF)).Experiments on reconstructing raw datasets including nonbiological,biological,and simulated samples demonstrate that our method has SR capability,high reconstruction speed,and high robustness to aberration and noise.

Digital generation of super-Gaussian perfect vortex beams via wavefront shaping with globally adaptive feedback

High-intensity vortex beams with tunable topological charges and low coherence are highly demanded in applications such as inertial confinement fusion(ICF) and optical communication. However, traditional optical vortices featuring nonuniform intensity distributions are dramatically restricted in application scenarios that require a high-intensity vortex beam owing to their ineffective amplification resulting from the intensity-dependent nonlinear effect. Here, a low-coherence perfect vortex beam(PVB) with a topological charge as high as 140 is realized based on the super-pixel wavefront-shaping technique. More importantly, a globally adaptive feedback algorithm(GAFA) is proposed to efficiently suppress the original intensity fluctuation and achieve a flat-top PVB with dramatically reduced beam speckle contrast. The GAFA-based flat-top PVB generation method can pave the way for high-intensity vortex beam generation,which is crucial for potential applications in ICF, laser processing, optical communication and optical trapping.

Multi-focus non-periodic scanning method for femtosecond lasers based on DMD and galvanometer scanners[Invited]

Multi-focus parallel scanning can effectively increase laser fabrication throughput.However,the conventional approach of using a spatial light modulator(SLM)to generate multi-foci and scan this fixed number of foci with galvanometer scanners can only achieve a periodic scanning trajectory due to the low switching speed of the SLM.Here we demonstrate a multifocus non-periodic scanning method for femtosecond lasers by using,instead,a fast-switching digital micromirror device(DMD)to generate a dynamic number of foci.The number of effective foci is quickly switched by introducing aberration to the undesired focus.In this way,the intensity allocated to each focus will not be affected by the number of foci,and a uniformity of 98%with different numbers of foci is achieved without adjusting the total laser energy.Finally,we validate the effectiveness of this scanning method by demonstrating corneal flap fabrication of porcine cornea in vitro.

Real-time gradation-expressible amplitude-modulationtype electroholography based on binary-weighted computer-generated hologram

In amplitude-modulation-type electroholography, the binary-weighted computer-generated hologram(BW-CGH) facilitates the gradation-expressible reconstruction of three-dimensional(3 D) objects. To realize real-time gradation-expressible electroholography, we propose an efficient and high-speed method for calculating bit planes consisting of BW-CGHs. The proposed method is implemented on a multiple graphics processing unit(GPU) cluster system comprising 13 GPUs. The proposed BW-CGH method realizes eight-gradation-expressible electroholography at approximately the same calculation speed as that of conventional electroholography based on binary computer-generated holograms. Consequently, we were able to successfully reconstruct a real-time electroholographic 3 D video comprising approximately 180,000 points expressed in eight gradations at 30 frames per second.