随机振动环境对微小型波前校正器性能的影响

波前校正器应用于空间光学系统必然要经历卫星动力学环境，随机振动环境是其中一个很重要的影响因素，采用有限元方法分析两种波前校正器在随机振动环境中的应力分布，结果表明所受应力均小于其材料的许用应力。器件结果未受破坏。随后对器件进行随机振动试验。试验后器件的几种主要性能均未受到影响，说明器件可承受均方根为6g的随机振动环境。     

数字式漏电流保护电路的设计与应用

1保护电路的总体设计1．1数字式漏电流表烧坏的原因 分析数字式漏电流表加装保护电路这一问题很早就被重视。自设备安装至现在，保护电路已作了几次修改，传统观点认为数字式漏电流表的损坏是由于输入信号过高造成的，因而设备安装初期几乎所有数字式漏电流表都安装了限压保护电路，但使用过程中发现这种办法无济于事，以后又加装了限流保护电路，效果仍不明显。     

自适应光学技术文献文摘与索引

本文评论了包括多元高频振动COAT、锐度函数最大化和相位共轭在内的基本自适应光学技术。叙述了自适应波前补偿系统的设计,并重点叙述了波前探测器和波前校正器。特别考虑了一种径向Ronchi光栅横向剪切千涉仪波前探测器。研究了目前正使用的自适应光学系统。     

基于SG3525控制的车载逆变电源设计

介绍一种基于SG3525控制的车载逆变电源的工作原理和电路设计.主电路采用典型两级变换的逆变结构:第1级变换通过SG3525控制器产生高频脉冲宽带调制(PWM)波,对输入信号升压整流;第2级变换通过NE556和CD4013芯片搭建逆变控制电路,将直流信号变换成工频信号;设计电池过压、欠压,输出过流、过热和输出欠压等保护电路.经验证该逆变电源具有可靠性高、电路简单、体积小等优点.     

自适应光学技术进展——1991年SPIE国际光学应用科学和工程讨论会综述

SPIE(国际光学工程学会)的1991年国际光学应用科学和工程讨论会上,发表了大批有关自适应光学系统和元件的论文,反映了自适应光学近年来获得的新进展。本文综合报导该讨论会的内容,包括能动光学系统、激光发射和成象观测自适应光学系统、波前探测器、波前校正器和能动光学器件以及激光导引星等。本文还报导自适应光学的发展动向和近年来的新突破。     

IGBT串联均压电路设计及仿真

为了解决IGBT串联运行时的电压不均衡问题,设计出了一种栅极侧动态均压控制电路,并建立了一个由三只IGBT串联组成的斩波仿真电路,通过模拟电压失横现象,验证了该均压电路的可行性。     

电路模拟结构在结构吸波材料中的应用探索研究

研究了电路模拟结构(电路屏)在结构吸波复合材料中应用的可行性。重点研究了电路屏结构尺寸、电路屏所处位置及复合材料体系各层中吸收剂配比对吸波特性的影响，结果表明，电路屏在雷达吸波材料中起到了以下的作用：电路屏能引起入射电磁波与反射电磁波的干涉，起到又一反射屏的作用；电路屏的加入能增大吸波结构的表面输入阻抗。通过合理的设计电路屏及使电路屏结构尺寸与吸波结构中的介质层相匹配，电路模拟结构可以有效地提高吸波结构的吸波性能。     

高稳定度直流恒流源的设计

高精度直流电位差计UJ52型所使用的专用高稳定度直流恒流源，其设计采用六节锌汞电池作为恒流源基准。由于该电池极易损坏（正常使用时每年都需换新），而且其他部件损坏在本地无法购置，使仪器·的使用受到极大的影响，故设计一高稳定度恒流源电路以代替原电路，是非常必要的。1电路设计原理电路设计采用了两级稳压稳流结构，首先由两稳压管LM7815和LM7915输出30V稳定的直流电压，尔后由低噪声、低漂移运算放大器Opo7等组成恒流输出的控制部分所控制。电路。设计的关键是采用了Lto99高精度基准电压源.作为恒流源的基础。LMi99为自带温…     

三位半数字万用表的故障检修

本人通过检修三位半数字万用表发现 ,此类表损坏的原因大多为使用者操作不当。以ＤＦ -８９０型数字万用表为例 ,仪表损坏的主要器件有 :①Ａ／Ｄ转换器ＩＣＬ７１０６或ＩＣＬ７１３６损坏。②运算放大器ＴＬ０６２损坏。③双时基电路ＩＣＭ７５５６损坏。④四与非门ＣＤ４０１１损坏。⑤电阻档过压保护电路的三极管Ｑ１（Ｃ９０１４）及保护电阻ＰＯ１（１ ５ｋΩ）损坏。⑥电容Ｃ９（３５Ｖ、０ ３３μＦ）漏电 ,导致基准电压变化 ,引起测量误差。下面具体介绍检修方法。１ 检修电源故障流程数字表检修工作一般先从电源开始 ,开关接通后 …     

一种用于声呐发射机的超级电容被动均压简易实用电路

超级电容器的性能不一致性会造成处于串联模式的电容组中个别电容器首先发生过压失效,进而加速整个储能组的失效。现有的均压电路一般工作在线性状态,电路也较复杂,不便于调试和生产。介绍了一种仅由5个元器件组成的简易、实用、高效的开关型被动均压电路,分析了其工作原理及均压特性。该电路在声呐发射机的储能电源中可长期使用,很好地保护了超级电容组。     

Reflective liquid crystal wavefront corrector used with tilt incidence

To allow angular separation of the beam reflected off a liquid crystal wavefront corrector from the incident beam, it is convenient to introduce a small incident angle. This avoids using a beam splitter and the associated energy losses. The effect of the tilt incidence on the liquid crystal wavefront corrector was investigated in this paper. For a parallel aligned liquid crystal wavefront corrector, a simplified model was established and used to analyze the change of the phase modulation under the tilt incidence. The simulated results showed that the effect of the tilt incidence on the phase modulation can be ignored when the angle of tilt incidence is less than 6 degrees. The phase modulation related to the incident angle was measured and the changing trend was similar to the calculated results. The effect of the tilt incidence on the diffraction efficiency of the liquid crystal wavefront corrector was also discussed. The simulated results indicated that the reduction of the diffraction efficiency is less than 1% for incidence angles under 3 degrees. Last, a closed loop correction experiment was done with an incident angle of 1 degrees. After correction, the averaged peak to valley (PV) and root mean square (RMS) of the wavefront were down to 0.15 lambda and 0.03 lambda, respectively, and a resolvable image was acquired.     

Optimization of sensing parameters for a confocal signal-based wavefront corrector in microscopy

The accuracy of a confocal signal-based wavefront corrector depends on several parameters such as spatial variation of optical properties within the specimen, aberration magnitude and composition, time required for the correction, etc. Here, a numerical analysis has been performed with the aim to improve system performance. The goal of the search algorithm in a confocal signal-based wavefront corrector is to estimate the Zernike coefficients of the aberrations. High-magnitude aberrations show low Strehl ratios. Repeating the correction process results in higher Strehl ratios, but at the cost of increased time. An in-focus on-axis specimen results in higher Strehl ratio compared to an out-of-focus and off-optical-axis specimen. For all cases, the wavefront correction accuracy is better, when the diameter of the pinhole is chosen to be equal to that of the Airy disk. The lower limit on the pinhole size for detecting small magnitude aberrations is set by noise.     

Adaptive optics technique to overcome the turbulence in a large-aperture collimator

A collimator with a long focal length and large aperture is a very important apparatus for testing large-aperture optical systems. But it suffers from internal air turbulence, which may limit its performance and reduce the testing accuracy. To overcome this problem, an adaptive optics system is introduced to compensate for the turbulence. This system includes a liquid crystal on silicon device as a wavefront corrector and a Shack-Hartmann wavefront sensor. After correction, we can get a plane wavefront with rms of about 0.017 lambda (lambda=0.6328 microm) emitted out of a larger than 500 mm diameter aperture. The whole system reaches diffraction-limited resolution.     

Application of eigenmode in the adaptive optics system based on a micromachined membrane deformable mirror

The construction process and characteristics of a deformable mirror eigenmode are introduced. The eigenmode of a 37-element micromachined membrane deformable mirror (MMDM) from OKO, Ltd. is analyzed. The Gaussian-Seidel low-order aberrations are fitted with eigenmodes as basic functions. An experimental adaptive optics (AO) system is constructed with the MMDM as the wavefront corrector, a deformable mirror eigenmode as the wavefront control algorithm, and a Shack-Hartmann wavefront sensor as the wavefront detector. The experimental results demonstrate that the deformable mirror eigenmode can act as the wavefront control algorithm for the AO system based on the MMDM.     

Fabrication error analysis and experimental demonstration for computer-generated holograms

Aspheric optical surfaces are often tested using computer-generated holograms (CGHs). For precise measurement, the wavefront errors caused by the CGH must be known and characterized. A parametric model relating the wavefront errors to the CGH fabrication errors is introduced. Methods are discussed for measuring the fabrication errors in the CGH substrate, duty cycle, etching depth, and effect of surface roughness. An example analysis of the wavefront errors from fabrication nonuniformities for a phase CGH is given. The calibration of these effects for a CGH null corrector is demonstrated to cause measurement error less than 1 nm.     

Requirements for discrete actuator and segmented wavefront correctors for aberration compensation in two large populations of human eyes

Numerous types of wavefront correctors have been employed in adaptive optics (AO) systems for correcting the ocular wavefront aberration. While all have improved image quality, none have yielded diffraction-limited imaging for large pupils (>/=6 mm), where the aberrations are most severe and the benefit of AO the greatest. To this end, we modeled the performance of discrete actuator, segmented piston-only, and segmented piston/tip/tilt wavefront correctors in conjunction with wavefront aberrations measured on normal human eyes in two large populations. The wavefront error was found to be as large as 53 microm, depending heavily on the pupil diameter (2-7.5 mm) and the particular refractive state. The required actuator number for diffraction-limited imaging was determined for three pupil sizes (4.5, 6, and 7.5 mm), three second-order aberration states, and four imaging wavelengths (0.4, 0.6, 0.8, and 1.0 microm). The number across the pupil varied from only a few actuators in the discrete case to greater than 100 for the piston-only corrector. The results presented will help guide the development of wavefront correctors for the next generation of ophthalmic instrumentation.     

Stressed liquid-crystal optical phased array for fast tip-tilt wavefront correction

A liquid-crystal optical phased-array technology that uses stressed liquid crystals provides a new type of tip-tilt wavefront corrector. It demonstrates a very fast time response (10 kHz) and high beam-steering efficiency (approximately 91%). The new technology presented here will allow for a nonmechanical, high-speed correction with simple device construction.     

Some regulated power supply apparatus using the Morgan circuit

The SCR chopper circuit has a very wide range of application in regulating a dc power, and its merits are universally appreciated. Because of its merits, the circuit is most suitable for a nonfailure power source that supplies power from a set of rectifier-batteries to a communication equipment or any other electronic equipment, which requires a dc power source of several output voltages. For such purposes, the output voltage of the circuit should be smooth, accurately regulated, and should respond quickly; at the same time, the efficiency must be high and reliability excellent. This paper offers, firstly, some improvements on the Morgan circuit in order to make it peculiarly suitable for different kinds of practical applications; namely, the smoothing filter is made as small as possible to make the response of the circuit rapid, while the efficiency is kept high. Secondly, data, obtained through the analysis of the operation in the case of the small filter, are presented. Thirdly, the paper shows, as the result of such analysis, that if a saturable current transformer (SCT) is designed properly, the circuit will behave as a self-regulating constant voltage power source. Lastly, it proposes a practical application which has a suitable protecting circuit composed of some simple circuit elements providing against the failure of commutation which causes a severe overvoltage and overcurrent to the load.     

Open-loop correction of horizontal turbulence: system design and result

Adaptive optics systems often work in a closed-loop configuration due to the hysteretic and nonlinearity properties of conventional deformable mirrors. Because of the high-precision wavefront generation and nonhysteretic properties of liquid-crystal devices, the open-loop control becomes possible. Open-loop control is a requirement for advanced adaptive optics concepts. We designed an open-loop adaptive optics system with a liquid-crystal-on-silicon wavefront corrector. This system is simple, fast, and can save much more light compared to conventional liquid-crystal-based closed-loop systems. The detailed principle, construction, and operation are discussed. The 500 m horizontal turbulence correction experiment was done using a 250 mm telescope in the laboratory. The whole system can reach a 60 Hz correction frequency. Evaluation of the correction precision was done at closed-loop configuration, which is 0.2 lambda (lambda=0.633 microm) in peak to valley. The dynamic image under open-loop correction got the same resolution compared to closed-loop correction. The whole system reached 0.68 arc sec resolution capability at open-loop correction, which is slightly larger than the system's diffraction-limited resolution of 0.65 arc sec.     

Active optics null test system based on a liquid crystal programmable spatial light modulator

We present an active null test system adapted to test lenses and wavefronts with complex shapes and strong local deformations. This system provides greater flexibility than conventional static null tests that match only a precisely positioned, individual wavefront. The system is based on a cylindrical Shack-Hartmann wavefront sensor, a commercial liquid crystal programmable phase modulator (PPM), which acts as the active null corrector, enabling the compensation of large strokes with high fidelity in a single iteration, and a spatial filter to remove unmodulated light when steep phase changes are compensated. We have evaluated the PPM's phase response at 635 nm and checked its performance by measuring its capability to generate different amounts of defocus aberration, finding root mean squared errors below λ/18 for spherical wavefronts with peak-to-valley heights of up to 78.7λ, which stands as the limit from which diffractive artifacts created by the PPM have been found to be critical under no spatial filtering. Results of a null test for a complex lens (an ophthalmic customized progressive addition lens) are presented and discussed.