基于数字全息的单透镜表面轮廓检测

为了对光学元件的三维面型进行检测,提出了用数字全息的方法实现单透镜的非接触无损、高效率检测。首先构建了离轴透射式数字全息系统,采用角谱算法对数字全息图进行再现,然后采用HRO相减法消除零级衍射干扰像,提高全息图质量,利用最小二乘法对相位进行解包裹,进而获取透镜的三维轮廓信息。实验结果表明,数字全息技术能有效获取光学元件表面轮廓信息。     

基于菲涅耳近似实现数字全息相位再现的误差分析及抑制

探讨了菲涅耳近似算法实现数字全息相位再现的误差及抑制技术.理论分析了基于菲涅耳近似算法实现全息相位再现所包含的误差项,计算机模拟了数字离轴全息图的记录和相位再现结果.在此基础上,模拟分析了离焦误差、数字再现光波误差及样本深度对相位再现的影响.针对记录参考光波和光学器件所引入的相位误差及其不定性,提出了利用相位相减全息图处理方法加以消除,并给出了实验结果加以验证.模拟分析结果表明,菲涅耳近似算法误差、离焦误差、数字再现光波倾斜误差、解包裹错误对相位再现结果都有不同程度的影响,相位相减全息图处理方法可以减小再现相位误差至0.4%.对记录过程、再现参数选择和处理方法都进行严格控制或适当选取,可得到高精度的再现结果.     

数字全息相位再现误差分析及抑制技术

为实现基于数字全息的三维轮廓测量,本文探讨了菲涅耳近似算法实现数字全息相位再现的误差及抑制技术。首先理论分析了基于菲涅耳近似算法实现全息相位再现所包含的误差项,然后计算机模拟了数字离轴全息图的记录和相位再现结果,在此基础,模拟分析了离焦误差、数字再现光波误差及样本深度对相位再现的影响。针对记录参考光波和光学器件所引入的相位误差及其不定性,本文提出利用相位相减全息图处理方法加以消除,并给出了实验结果加以验证。模拟分析结果表明,菲涅耳近似算法误差、离焦误差、数字再现光波倾斜误差、解包裹错误对相位再现结果都有不同程度的影响。若获得高精度的再现结果,对记录过程、再现参数选择和处理方法都要进行严格控制或适当的选取。     

预放大数字全息系统记录距离的设计

在数字全息显微术中,为了获得非重叠、高质量再现像,需要设置合理的记录距离。本文结合再现条件与记录条件进行较全面地分析设计,即在考虑采样定理、频谱分离条件之外,还研究了光学传递函数离散条件和再现像与放大像之间的尺寸关系,进而更精确地得到了预放大数字全息系统记录距离的设置方法。以USAF1951分辨率板为样本,分别以记录距离为50.50,134.20和140.30mm进行实验,结果表明,当记录距离不考虑放大像与再现像之间尺寸关系时,利用菲涅尔衍射法获得的再现像模糊;当记录距离考虑光学传递函数离散条件时,利用卷积法再现能获得清晰再现像;当记录距离同时满足再现条件和记录条件时,数值再现能获得高质量的再现像,且能分辨分辨率板的7.6组条纹,即横向分辨力达到2.19μm,进一步论证了所提需要考虑再现像与放大像之间的尺寸关系和光学传递函数离散条件来设计记录距离的方法更精确。通过理论推导和实验验证了所提的设计记录距离的方法较全面、给出的记录距离范围较合理,为数字全息显微术获得高质量的再现像提供了保障。     

高精度离轴凸非球面反射镜的加工及检测

为了提高离轴凸非球面反射镜的面形精度和光轴精度,研究了离轴凸非球面反射镜的加工与检测技术。首先,描述了离轴三反消像散(TMA)光学系统以及作为该光学系统次镜的离轴凸非球面反射镜的光学参数和技术指标。然后,介绍了非球面计算机控制光学表面成型(CCOS)技术及FSGJ非球面数控加工设备。最后,给出了非球面研磨阶段检测用的轮廓测量法和离轴凸非球面抛光阶段检测用的背部透射零位补偿检测法,并对背部透射零位补偿检测中离轴凸非球面反射镜光轴精度的控制技术进行了研究。检测结果表明:采用背部透射零位补偿检测法检测得到的离轴凸非球面反射镜的面形精度为0.017λ(均方根值,λ=0.632 8μm);用Leica经纬仪测量反射镜的光轴精度其结果达到9.4″,满足光学设计技术指标要求。     

大视场相机光轴垂直度对定位误差的影响研究

为了实现影像测量仪双相机的精确定位,以满足批量多种类零件自动化测量需求,在现有的影像测量仪上引入由大视场相机构成的视觉引导模块。但由于人工安装误差,很难保证大视场相机光轴与被测量零件完全垂直,利用大视场相机对标定板的Mark点进行特征提取,然后改变被测物与平台的倾斜角度,使用图像处理软件及数学模型建立光轴倾斜角度与像素当量的数学函数关系式,实现了光轴垂直度的矫正,并得到X和Y轴方向角度允许偏转范围分别为2.08°和2.07°。实验结果表明了方法的有效性,降低了对人工安装的技术要求。使元件组装密度最小距离0.4 mm优化到了0.2mm,提高了元件的测量精度。     

光学元件表面疵病检测仪的精度建模及预测

为了对疵病检测仪的精度进行预测并对设计方案的合理性进行验证,基于多体系统理论对疵病检测仪机械运动机构进行了精度建模。用低序体阵列和拓扑结构描述了疵病检测仪的结构特点,提出了疵病检测仪的精度模型,针对光学系统的要求进行了误差分离。基于该精度模型,以典型光学元件为例提出了误差补偿的计算流程,对疵病检测仪的精度进行预测。预测结果表明,光学探头的成像点与待测点沿光学探头光轴方向误差最大值为3.0μm,满足光学探头景深20μm的检测要求,同时光学探头成像点与光学元件待测点垂直于光轴方向误差及光学探头光轴与光学元件待测点处表面法向的夹角均在设计指标内。     

投影光刻离轴照明用衍射光学元件设计

离轴照明（OAI：Off-axis Illumination）作为一种重要的分辨率增强技术（RET：Resolution Enhancement Technology）被广泛的应用于投影光刻系统。使用衍射光学元件（DOE：Diffractive Optical Element）作为光刻照明系统的光束整形器件,能够在保持较高照明效率的基础上精确控制离轴照明光束的形状及光强分布。本文利用基于傅立叶变换的分步迭代方法进行了该类DOE的优化设计。DOE采用了多台阶位相结构,设计所得8台阶DOE设计结果分别实现了偶极、四极、环形及Bulls-Eye等照明方式,其照明效率都达到了80%以上,与目标光强分布的均方根偏差均小于7％。     

飞秒激光跟踪仪光轴与竖轴同轴度的标定

考虑飞秒激光跟踪仪仪器轴系的几何误差会影响仪器的指向精度并最终影响坐标测量精度,本文研究了激光光轴与竖轴的几何误差对仪器测量精度的影响。提出了激光光轴与竖轴的同轴度标定方法,以降低其不重合带来的跟踪测量误差。首先,基于几何光学原理建立了光轴与竖轴的几何误差模型,分别分析了光轴与竖轴的倾斜与平移误差对仪器测角精度的影响。然后,针对设计的仪器提出了基于旋转成像原理的光轴与竖轴同轴度的检测方法,并设计了一套同轴度检测装置。最后,基于该检测装置,通过调节两组双光楔完成了激光光轴与竖轴的倾斜与平移误差的标定。结果显示,经标定校准后激光光轴与竖轴的角度误差为3.4″;平移误差为26.1μm,得到的结果为仪器后续建立误差补偿模型奠定了基础。     

用数字全息术检测轮胎气泡缺陷

提出了一种基于二次曝光数字全息干涉术的子午线轮胎内部气泡缺陷无损检测方法.该方法利用数字全息记录系统记录下轮胎初始状态和受热膨胀变形状态的数字全息图,在计算机中对这些数字全息图分别再现后,将代表轮胎变形状态的再现波前与其初始状态的再现波前进行干涉,获得携带轮胎变化信息的干涉条纹和相位分布;分析了存在气泡缺陷区域的轮胎和无缺陷轮胎两种情况下的干涉条纹及其相位分布的特点和区别.分析结果表明:在轮胎内部存在缺陷的位置,其二次曝光数字全息干涉条纹具有与质量正常位置处干涉条纹相对独立的特征,该方法可以检测出轮胎气泡缺陷,记录系统的横向分辨率为16.4 μm.     

高斯涡旋光束通过像散透镜后的相位奇异特性

光场相位奇异特性研究在奇点光学研究领域中具有非常重要的意义。本文运用广义惠更斯-菲涅尔衍射积分公式推导出高斯涡旋光束通过像散透镜后的光场分布表达式,并研究了它在几何焦平面上的相位奇异特性。结果表明,高斯涡旋光束通过像散透镜后在几何焦平面上存在相位奇点,相位奇点受到透镜的像散系数、光束束腰宽度和涡旋离轴量等参数的影响。在一定条件下,几何焦平面上出现直刃型位错线或光涡旋。当像散系数为0时,光涡旋出现在y轴上。当像散系数不为0,而涡旋离轴量为0时,会出现直刃型位错线或光涡旋,且各自的位置都非常稳定。当像散系数、涡旋离轴量或束腰宽度改变时,光涡旋会发生移动。这对光学元器件的设计和涡旋光束相位奇点的控制有一定的参考价值。     

激光聚变冲击波被动式测速光学系统设计

针对激光聚变装置冲击波速度被动测量的需求,设计了一种测速光学系统。采用高紫外透过率的氟化玻璃,实现了透射式300～800nm复消色差设计。系统光路具有前后两组镜头,中间为平行光,镜头间距可变,光路适应能力强。系统前端两侧的双目机器视觉能够完成自动寻的。平行光路中设置5个激光器,轴上的1个前向照明靶点用来观察条纹相机狭缝处的目标像质,轴外的4个与光轴平行后向传输用来标识系统光轴的位置,激光器部件可电动切入/切出。系统前组镜头F/#数为4,宽谱工作物方分辨率优于10μm,532nm单波长工作物方分辨优于5μm。该光学系统光路排布灵活,可单独被动测速,也可与主动测速系统VISAR耦合构成主被一体复合测速系统,满足激光聚变装置冲击波测速的需求。     

Simultaneous in-plane and out-of-plane deformation measurement by speckle multi-recording method

An in-plane and out-of-plane deformation simultaneous measurement method using only two speckle patterns grabbed before and after deformation of an object with rough surfaces using two cameras has been proposed. However, there are some problems concerning the setup of optical system, the aspect ratio of grabbed image data and so on in the conventional method. To solve these problems, the new optical system is proposed by using the multi-recording technology. Though multi-recording technologies have been already employed conveniently in the off-axis digital holography, the technologies have not been used functionally enough in speckle interferometry. In this paper, an in-plane and out-of-plane deformation simultaneous measurement is performed by the proposed method based on multi-recording technology in speckle interferometry. From experimental results, it can be confirmed that the proposed optical system can measure simultaneously in-plane and out-of-plane deformations in high resolution by one camera.     

Quantification of micrometre-sized porosity in quasicrystals using coherent synchrotron radiation imaging

The ability to image phase distributions with high spatial resolution is a key capability of microscopy systems. Consequently, the development and use of phase microscopy has been an important aspect of microscopy research and development. Most phase microscopy is based on a form of interference. Some phase imaging techniques, such as differential interference microscopy or phase microscopy, have a low coherence requirement, which enables high‐resolution imaging but in effect prevents the acquisition of quantitative phase information. These techniques are therefore used mainly for phase visualization. On the other hand, interference microscopy and holography are able to yield quantitative phase measurements but cannot offer the highest resolution. A new approach to phase microscopy, quantitative phase‐amplitude microscopy (QPAM) has recently been proposed that relies on observing the manner in which intensity images change with small defocuses and using these intensity changes to recover the phase. The method is easily understood when an object is thin, meaning its thickness is much less than the depth of field of the imaging system. However, in practice, objects will not often be thin, leading to the question of what precisely is being measured when QPAM is applied to a thick object. The optical transfer function formalism previously developed uses three‐dimensional (3D) optical transfer functions under the Born approximation. In this paper we use the 3D optical transfer function approach of Streibl not for the analysis of 3D imaging methods, such as tomography, but rather for the problem of analysing 2D phase images of thick objects. We go on to test the theoretical predictions experimentally. The two are found to be in excellent agreement and we show that the 3D imaging properties of QPAM can be reliably predicted using the optical transfer function formalism.     

A laser sensor with multiple detectors for freeform surface digitization

An integrated laser scanning sensor for freeform surface digitization is presented. The sensor consists of a diode laser light source and four position-sensitive device (PSD) detectors. The stand-off distance of the sensor is 180 mm and the measurable range is 90 mm. The Lambert model is applied to calculate the displacement between the sensor and the measured point on the object surface along the optical axis, under the assumption of a diffusive surface. The inclination angle of the measured point from the vertical plane of the laser beam is calculated by mathematical inference. Those data are used in error compensation to improve system precision. The new design of multiple detectors could increase the measurable angle and could solve the dead space problem in single point laser of triangulation measurement. The computer simulation and actual measurements show that the displacement resolution reaches 50 μm, and the system performs well in regards to stability and repeatability. The sensor system could be mounted on the NC machine orX-Y platform for freeform surface digitization.     

长焦距离轴三反测绘相机的外场立体成像

在地面模拟了长焦距、宽视场离轴三反光学系统的在轨立体成像,通过对图像的数据处理和分析,验证了离轴三反测绘相机在轨立体成像的可行性。提出了长焦距离轴三反测绘相机外场立体成像的单点成像方法。在该方法中,单台离轴三反相机通过旋转转台对靶标成像,根据规划的相机交会角旋转靶标,并精确测量出靶标的旋转角度,通过靶标的旋转来模拟两线阵相机的相机夹角。在外场立体成像中,根据轨道高度、外场立体成像的物距及理论设计需达到的高程精度和平面精度设计地面靶标。最后,对成像方式进行处理,验证了离轴三反测绘相机立体成像的可行性;对提出的外方位元素、两相机最佳夹角的测量方法进行了精度分析。该单点成像方法具有实用价值,可用于长焦距离轴三反测绘相机在轨立体成像的可行性验证。     

可调焦离轴三反光学系统的装调

针对离轴反射光学系统的精密装调问题,提出了一种高精度空间交互测量以及基准传递系统,可实现调焦角度与系统光轴的高精度角度定位。该系统口径为450mm,可实现0.5km至无穷远的调焦,调焦角度精确定位后,只需调整无穷远处离轴三反光学系统的波像差满足要求,即可保证系统各个调焦位置处的波像差均满足设计要求,大大提高了装调效率。装调实验结果表明,无穷远处系统的波像差结果为0.09λ,1.5km处系统的波像差为0.1λ,2.5km处系统的波像差为0.11λ,0.5km处系统的波像差为0.2λ,均优于设计要求。     

A quantitative evaluation of degraded system resolution in an energy-dispersive X-ray spectrometer by activating the scanning coils in a (s)TEM

The system resolution of an energy-dispersive X-ray spectrometer in a combined transmission and scanning electron microscope was found to be degraded under some operating conditions. Degradation was only observed when the scanning coils were activated. It was worse at lower magnifications and rapid scan rates. Degradation also varied as a function of the distance of the detector from the electron-optical axis. The effect was attributed to electronic induction in the detector from the scanning coils of the microscope. An example of the effect of this error on quantitation showed that, using a 75 mmol kg^-1 calcium standard, a 13.5 eV broadening of the system resolution gave a 22% decrease of the apparent concentration. The severity of this effect was variable in other instrument/spectrometer combinations. Scanning coil-induced noise may go undetected unless there is an automatic evaluation of the system resolution of each spectrum.