基于空间光调制器的光束大角度扫描技术研究

为实现一束激光在90°锥形范围内的扫描,利用液晶空间光调制器在光束偏转控制时精度高、无机械惯性等优点,研究并建立了基于液晶空间光调制器的光束偏转和角放大光路系统。提出了空间光调制器的可编程相位调制算法和角放大光路结构,推导了空间光调制器光束偏转角度与相位灰度驱动图的关系,设计了角度放大倍率高于22倍的角放大光路系统。在此基础上,建立了光束扫描控制实验系统,对该装置角度出射范围进行了测量,将实际的角放大倍率与设计值进行对比。实验结果表明:研制系统的出射视场角可达91.22°,并可通过畸变校正实现出射视场角范围内的规则形状扫描。该研究在光束敏捷控制、无线激光通信、目标搜索与追踪等领域具有重要的研究价值和应用前景。     

多变视场的多焦点多光子激发荧光显微技术

发展了一种新型的多焦点多光子激发荧光显微技术,通过软件控制空间光调制器,在所需要的成像区域产生相应的激发光点阵,通过扫描入射角实现激发点阵快速并行扫描激发,通过CCD并行记录所产生的荧光信号,获得任意视场图像。分别实现了10×10和50×50点阵激发下的全视场双光子荧光图像,并且实现了同时多个区域寻址的多焦点激发成像。对比其他多焦点显微技术,该技术具有明显的灵活性,不但保持了多焦点激发的快速成像的优点,而且还增加了任意数量成像区域同时寻址和阵列点密度变化,所有这些变化只需要通过软件加载相应的相位图案给空间光调制器,而不需要任何硬件更改。     

激光显示中光学系统研究

为了满足机械转镜扫描要求(转镜转速每分钟不少于3万转)及光束与水平信号的行场同步要求，提出采用面阵空间光调制器及多像素并行扫描方式。采用“面阵空间光调制器”对激光束进行选通和光强调制，使覆盖多像素的激光束在高速扫过面阵空间光调制器时，光强按视频图像的强弱进行调制，从而形成激光视频图像。由于采用了多像素并行扫描、新型二维扫描转镜和积分器光路，扫描速度大大降低，由每分钟几万转降低到3000转，解决了扫描式激光显示的技术瓶颈和激光干涉条纹问题，获得了很好的显示效果。     

Multifocal multiphoton microscopy based on a spatial light modulator

We present a new multifocal multiphoton microscope that employs a programmable spatial light modulator to generate dynamic multifocus arrays which can be rapidly scanned by changing the incident angle of the laser beam using a pair of galvo scanners. Using this microscope, we can rapidly select the number and the spatial density of focal points in a multifocus array, as well as the locations and shapes of arrays according to the features of the areas of interest in the field of view without any change to the hardware.     

利用空间光调制器的偏振特性实现图像边缘增强

讨论了光电混合型范德卢格特相关器中起偏器和检偏器对场景空间光调制器的影响。提出了一种通过设置起偏器和检偏器相对于场景空间光调制器入射表面液晶指向矢方向的角度来实现图像边缘增强的预处理方法。通过对XGA2L11型电寻址薄膜晶体管驱动透射式液晶空间光调制器的实验测试表明,该方法减少了计算机图像预处理的运算量,有效地提高了目标识别的速度,实现了场景图像边缘增强的实时预处理。     

Ultrafast, large-field multiphoton microscopy based on an acousto-optic deflector and a spatial light modulator

We present an ultrafast, large-field multiphoton excitation fluorescence microscope with high lateral and axial resolutions based on a two-dimensional (2-D) acousto-optical deflector (AOD) scanner and spatial light modulator (SLM). When a phase-only SLM is used to shape the near-infrared light from a mode-locked titanium:sapphire laser into a multifocus array including the 0-order beam, a 136 μm × 136 μm field of view is achieved with a 60× objective using a 2-D AOD scanner without any mechanical scan element. The two-photon fluorescence image of a neuronal network that was obtained using this system demonstrates that our microscopy permits observation of dynamic biological events in a large field with high-temporal and -spatial resolution.     

Spatial Temporal Analysis of Electrically-Addressable Phase-Only Spatial Light Modulator

An optically addressed parallel-aligned nematic-liquid-crystal spatial light modulator (PAL-SLM) has been studied as a dynamic phase-only modulation device. A computer control feature of the spatial light modulator is strongly desired for practical applications. For those demands, an electrically-addressable phase-only spatial light modulator has been developed to combine a liquid crystal display (LCD) with a PAL-SLM (LCD-coupled PAL-SLM) and its performance has been reported. However, a temporal characteristic especially two-dimensional (2D) response has not been discussed before. In this paper, 2D response analysis system has been constructed by using a high-speed complementary Metal-Oxide-Semiconductor (CMOS) camera (1000 frames/sec) and the 2D-modulation characteristic of the LCD-coupled PAL-SLM has been observed. As a result, the LCD has a spatially non-uniform modulation characteristic due to a scanning addressing. It has the potential to cause problems in high speed switching for a computer generated hologram. On the other hand, the spatial non-uniformity has not been observed with the LCD-coupled PAL-SLM.     

Wavefront Shaping for Fast Focusing Light through Scattering Media Based on Parallel Wavefront Optimization and Superpixel Method

When light travels in biological tissues,it undergoes multiple scattering and forms speckles,which seriousl.y restricts the penetration depth of optical imaging in biological tissues.With wavefront shaping method,by modulating the wavefront of incident light to compensate for the wavefront aberration,light focusing and scanning imaging through scattering media can be achieved.However,wavefront shaping must be accomplished within the speckle decorrelation time.Considering the short speckle decorrelation time of living tissues,the speed of wavefront shaping is rather essential We propose a new iterative optimization wavefront shaping method to improve the speed of wavefront shaping in which the existing parallel optimization wavefront shaping method is improved and is combined with the superpixel method.Compared with the traditional multi-frequency parallel optimization method,the modulation rate of our method is doubled.Moreover,we combine the high frame rate amplitude modulator,i.e.,the digital micromirror device(DMD),with the superpixel method to replace the traditional phase modulator(i.e.,spatial light modulator),which further increases the optimization speed.In our experiment,when the number of the optical modes is 400,light focusing is achieved with only 1000 DMD superpixel masks and the enhancement factor reaches 223.Our approach provides a new path for fast light focusing through wavefront shaping.     

Stimulated emission depletion microscopy with a supercontinuum source and fluorescence lifetime imaging

We demonstrate stimulated emission depletion (STED) microscopy implemented in a laser scanning confocal microscope using excitation light derived from supercontinuum generation in a microstructured optical fiber. Images with resolution improvement beyond the far-field diffraction limit in both the lateral and axial directions were acquired by scanning overlapped excitation and depletion beams in two dimensions using the flying spot scanner of a commercially available laser scanning confocal microscope. The spatial properties of the depletion beam were controlled holographically using a programmable spatial light modulator, which can rapidly change between different STED imaging modes and also compensate for aberrations in the optical path. STED fluorescence lifetime imaging microscopy is demonstrated through the use of time-correlated single photon counting.     

Femtosecond pulse shaping using a two-dimensional liquid-crystal spatial light modulator

We introduce a programmable, high-rate scanning femtosecond pulse shaper based on a two-dimensional liquid crystal on a silicon spatial light modulator (SLM). While horizontal resolution of 1920 addressable pixels provides superior fidelity for generating complex waveforms, scanning across the vertical dimension (1080 pixels) has been used to facilitate at least 3 orders of magnitude speed increase as compared with typical liquid-crystal SLM-based pulse shapers. An update rate in excess of 100 kHz is demonstrated.     

Compression of fiber supercontinuum pulses to the Fourier-limit in a high-numerical-aperture focus

A multiphoton intrapulse interference phase scan (MIIPS) adaptively and automatically compensates the combined phase distortion from a fiber supercontinuum source, a spatial light modulator pulse shaper, and a high-NA microscope objective, allowing Fourier-transform-limited compression of the supercontinuum pulses at the focus of the objective. A second-harmonic-generation-based method is employed to independently validate the transform-limited compression. The compressed pulses at the focus of the objective have a tunable duration of 10.8-38.9 fs (FWHM), a central wavelength of ~1020 nm, an average power of 18-70 mW, and a repetition rate of 76 MHz, permitting the application of this source to nonlinear optical microscopy and coherently controlled microspectroscopy.     

基于液晶纯相位光调制器的4f系统去噪方法

分析了4f系统的噪声来源,提出使用液晶空间光调制器实时去除系统噪声.通过使用Zemike多项式拟合透镜等光学器件引入的像差,根据液晶纯相位光调制器利用位相共轭波进行静态波面校正的工作原理,提出了一种新的相位校正算法,模拟仿真美国BNS公司反射式256×256纯相位液晶空间光调制器,通过重构并逼近畸变波面,产生相位共轭波...     

Spectral-domain optical coherence phase and multiphoton microscopy

We describe simultaneous quantitative phase contrast and multiphoton fluorescence imaging by combined spectral-domain optical coherence phase and multiphoton microscopy. The instrument employs two light sources for efficient optical coherence microscopic and multiphoton imaging and can generate structural and functional images of transparent specimens in the epidirection. Phase contrast imaging exhibits spatial and temporal phase stability in the subnanometer range. We also demonstrate the visualization of actin filaments in a fixed cell specimen, which is confirmed by simultaneous multiphoton fluorescence imaging.     

Holographic Three-Dimensional Display Using an Electron-Beam-Addressed Spatial Light Modulator

Three-dimensional (3-D) or holographic information extracted by two-dimensional active optical heterodyne scanning has been demonstrated recently. The technique is called optical scanning holography. To reconstruct the obtainable 3-D holographic information, digital techniques have been used and demonstrated. For real-time applications, we need to investigate spatial-light-modulator-based systems. In this paper, we first briefly review optical scanning holography, and then present experimental results of 3-D image reconstruction using an electron-beam-addressed spatial light modulator.     

Fiber-optic confocal microscopy using a spatial light modulator

We present a novel fiber-optic confocal microscope in which the scanning operation is achieved by use of a spatial light modulator (SLM) to sequentially illuminate individual fibers or patterns of multiple fibers. Experimental images are presented, and the optical-sectioning capability of the device is demonstrated. The novel SLM-based system is more optically efficient, achieves higher contrast, and has improved optical-sectioning capabilities compared with those of other proposed instruments for confocal microendoscopy.     

利用光束整形器件阵列消除电寻址空间光调制器的"黑栅"效应

研究了电寻址空间光调制器中由于低开口率所引起的"黑栅"效应对图像质量的影响。提出了一种基于纯相位型光束整形器件阵列的"黑栅"消除方法,并分析了该方法的基本原理。介绍了用Gerchberg Saxton相位恢复算法来设计光束整形器件的基本思路,给出了光束整形的结果。理论分析及仿真计算表明,该方法能有效地消除电寻址空间光调制器相邻像素之间的黑带。     

Efficient image projection by Fourier electroholography

An improved efficient projection of color images is presented. It uses a phase spatial light modulator with three iteratively optimized Fourier holograms displayed simultaneously--each for one primary color. This spatial division instead of time division provides stable images. A pixelated structure of the modulator and fluctuations of liquid crystal molecules cause a zeroth-order peak, eliminated by additional wavelength-dependent phase factors shifting it before the image plane, where it is blocked with a matched filter. Speckles are suppressed by time integration of variable speckle patterns generated by additional randomizations of an initial phase and minor changes of the signal.     

Spatial and Temporal Properties of a Nonlinear Optical Feedback System

We experimentally investigate the spatial and temporal properties of a nonlinear optical system composed of an optically addressed spatial light modulator and a two-dimensional optical feedback. The system property is examined using fringes with only one spatial wave vector. The fringes are spontaneously generated using a spatial frequency filter in the optical feedback. We also experimentally investigate the properties of the spatial light modulator in the system using ordinary interference fringes in order to compare with the system property. We demonstrate that the spatial frequency response of the nonlinear optical system is identical to that of the spatial light modulator. We also demonstrate the distinctive temporal behavior of diffraction lights from the fringes generated in the system.     

Real-time, whole-field speckle photography using a bistable optically addressed spatial light modulator

The application of a bistable optically addressed spatial light modulator for real-time visualization of solid-body displacement fields is described. Double-exposure speckle patterns are recorded on the spatial light modulator and a whole-field filtering technique is used to generate fringes of constant displacement.     

基于石墨烯的宽带全光空间调制器

提出了单层石墨烯包裹微纳光纤的全光空间调制.石墨烯作为可饱和吸收体包裹在通过二氧化碳激光器加热制备的微纳光纤上,当信号光沿着微纳光纤传输时部分光将以倏逝场的形式沿着微纳光纤表面传递,并与石墨烯产生作用被吸收.同时将波长为808 nm的抽运光从空间垂直入射到石墨烯包裹的微纳光纤处,依据石墨烯的优先吸收特性,通过抽运光控制石墨烯对信号光的吸收,实现了宽带全光空间调制.在1095 nm波长处获得最大调制深度约为6 dB,调制带宽约为50 nm,调制速率约为1.5 kHz.空间全光调制器具有输出信号光“干净”的特点.与传统石墨烯微纳光纤全光调制器相比,输出端不需要对抽运光进行光学滤波而直接获得已调信号.该复合波导全光空间调制器以更为灵活、高效的方式打开了微纳超快信号处理的大门.