光学自由曲面数控化加工方法

在光学系统中，为了满足特殊的成像要求，需要使用自由曲面光学零件，但由于自由曲面是一类非常复杂的曲面，用传统的光学加工方法很难加工。本文概要介绍了光学非球面的多种加工方法，探索了这些方法加工光学自由曲面的可能性，提出了用数控化加工方法加工光学自由曲面，并利用这种方法加工了一块自由曲面透镜。     

光学自由曲面的检测方法

针对自由曲面光学元件离轴像差小,应用广泛,但检测难度大,加工精度不够高等特点,对现行的自由曲面光学检测方法进行了分析。提出了在自由曲面光学元件的不同加工阶段宜采用不同的检测手段,根据加工的步骤依次采用三坐标机、轮廓仪、光学干涉测量等方法为好。介绍了子孔径拼接技术的发展,叙述了利用计算全息(CGH)和反射光栅摄影测量法检测光学自由曲面等两种有着良好发展前景的方法。最后,给出了利用CGH检测三次位相板的实例。     

光学自由曲面的检测方法

针对自由曲面光学元件离轴像差小，应用广泛，但检测难度大，加工精度不够高等特点，对现行的自由曲面光学检测方法进行了分析。提出了在自由曲面光学元件的不同加工阶段宜采用不同的检测手段，根据加工的步骤依次采用三坐标机、轮廓仪、光学干涉测量等方法为好。介绍了子孔径拼接技术的发展，叙述了利用计算全息（CGH）和反射光栅摄影测量法检测光学自由曲面等两种有着良好发展前景的方法。最后，给出了利用CGH检测三次位相板的实例。     

基于加工公差约束的自由曲面棱镜设计

自由曲面棱镜是轻型头盔显示系统的核心光学器件,其巧妙的设计以及精密的加工方法历来备受研究者的关注。目前有关自由曲面棱镜的研究主要集中于视场角和成像质量上,而忽略了公差设计,尤其是加工误差对棱镜的影响。针对这一现象,在详细分析了自由曲面棱镜的加工误差来源之后,提出了基于公差约束的自由曲面棱镜优化设计方法,以保证在加工精度允许的前提下得到最佳的成像质量。通过光学仿真实验及成像质量分析,验证了该方法的有效性。     

渐进多焦点眼用镜片的加工制造

以渐进多焦点镜片的加工为实例,阐述了采用CNC雕刻机(En3d)加工自由曲面光学元件的加工工艺,利用TRACEPRO软件宏语言将点阵数据生成非均匀有理B样条自由曲面,运用精雕机的JDPaint软件生成刀具路径,对自由曲面光学元件进行加工制造.利用自由曲面面形测量仪对加工完成的渐进多焦点镜片进行光焦度分布和散光分布的面形分析.实验结果表明:采用CNC雕刻机加工自由曲面光学元件的加工工艺简单,操作方便,并且加工后的渐进多焦点镜片面形符合设计要求.     

准直型自由曲面LED二次光学元件设计与加工

提出了一种准直型LED自由曲面二次光学元件的设计方法,基于光线追迹,满足光学元件的光学要求和曲面连续性的几何要求,简化了自由曲面设计过程,实现程序化设计。自由曲面的应用以能够实现自由曲面的制造为前提,基于自由曲面的可加工性,提出设计方法可结合加工需求灵活更改设计参数,设计自由度高,实验验证了设计方法的正确性。     

渐进自由曲面镜片光学性能仿真方法研究

提出了一种渐进自由曲面镜片的光学性能仿真方法,能够在镜片的设计阶段对镜片的光焦度和散光分布进行仿真分析。采用双三次样条曲面拟合法,通过计算自由曲面镜片面型离散点数据局部点云拟合曲面的函数,得到曲面上各点的主曲率,进而得到渐进自由曲面镜片的光焦度和散光分布。结果显示仿真方法得到的镜片光焦度和散光分布图与基于莫尔偏折法原理的FFV软件仿真和实际加工得到镜片的测量结果相类似。     

基于自由曲面的产生五向准直光束的元件

为了实现光束沿多向准直出射的要求,提出了基于自由曲面的光学器件设计方法。该光学器件是四个侧面为自由曲面、上表面为准直透镜的空心梯形台。基于微分几何理论和折射定律,建立梯形台侧面轮廓曲线上的点所满足的方程,结合Matlab软件数值计算出自由曲面轮廓曲线的离散数据点,将数据点导入Solidworks中进行曲线拟合并建模,进而得到梯形台侧面的实体模型;运用CodeⅤ软件设计出上表面准直透镜。将自由曲面面型数据和准直透镜数据导入到Lighttools软件中进行了仿真模拟,结果表明,该光学器件可实现光线五向准直出射。     

自由曲面光学元件待加工区域标记方法

提出了一种使用三坐标测量机(CMM)对自由曲面光学元件表面待加工区域进行标记的方法。针对自由曲面光学元件外形特征设计工件坐标系,规划工件坐标系定位点,通过坐标变换将待加工区域的像素坐标转换为对应的自由曲面工件坐标系的标记点位置坐标,将待加工区域的感兴趣点三维坐标导入CMM,使用CMM对工件坐标系下标记点位置自动探测,实现待加工区域的标记,提高了检测效率也避免人为标记定位误差。     

基于超精密机床的光学自由曲面原位测量方法

原位测量是提高光学自由曲面面形精度的重要手段,对于提高加工效率、实现加工过程自动化具有重要意义。由于面形的复杂性,光学自由曲面原位测量一直是超精密测量领域的难题。提出了一种基于超精密机床的光学自由曲面原位测量方法,测量系统由LVDT气浮式传感器、红宝石探针和数据采集部件组成,采用螺旋线方式进行加工及测量路径的设计,通过运动控制接口实现机床坐标和测量数据的实时同步采集,快速精确地获取测量数据。实验结果表明,所加工的双正弦自由曲面的面形误差在±0.5μm范围内。     

自适应光学对大气扰动波前的补偿效果研究：I.理论推导

在采用冻结湍流假设和几何光学近似的条件下，得到了经自适应光学系统校正后的剩余波前相位扰动的结构函数，进而根据剩余相位结构函数与系统Ｓｔｒｅｈｌ比的关系，求出自适应光学系统的补偿效果受系统的时空传递函数，大气湍流，光波传播路径上的横向风，观察目标的旋转角速度以及系统时间延迟影响情况的解析表达式。     

全息柱面光栅的设计及其在立体显示技术的应用

根据傅里叶全息光学的基本原理与柱面光栅的分光特性,提出了用马赫-曾德尔光路制作柱面光栅的方法,用其实现图像的立体化.全息柱面光栅是全息术与图像立体化技术的有机结合,制作方法简单,具有一定的实用价值.     

平面反射镜反射率检测系统研究

为实现在高功率激光装置中对平面反射镜反射率的高精度测量,提出了将双光束分光光度法与VW测量法相结合,利用扩束后的测量光束测量被测元件的反射率.推导了计算公式,搭建了测量光束口径为50mm的检测系统,通过对标准吸收玻璃吸收值的测试验证了系统对光束能量测试的准确性.利用该系统对高功率激光装置使用的反射镜的反射率进行了测量,...     

Phase diversity for calibrating noncommon path aberrations of adaptive optics system under nonideal measurement environment

When the defocus cannot be measured and the wavefront solution set is restricted by a multi-channel, some practical problems exist in the calibration of the noncommon path aberrations of the adaptive optics system. To solve these problems, an evaluation function of phase diversity algorithm is constructed in this paper. We use the method that the estimated aberration and the modulated deformable mirror iterate each other to make up the nonideal measurement environment. Then the ill-pose problem of the solution by phase diversity, produced as relaxing constraints of the diversity defocus on the wavefront solution set, is solved. We have adopted the proposed method to measure the noncommon path aberrations of the adaptive optics system on a 1.23 m telescope. Experimental results demonstrate that wavefront solution is more accurate and the whole imaging quality is improved effectively by using the deformable mirror to compensate the aberration measured.     

Application of iterative path revision technique for laser cutting with controlled fracture

Laser cutting using the controlled fracture technique has great potential to be employed for the ceramic substrate machining. The heat produced on the surface of a ceramic substrate by the laser separates the substrate controllably along the moving path of the laser beam. Because the extension of the breaking frontier is lager than the movement of the laser spot, the actual fracture trajectory deviates from the desired trajectory when cutting a curve or cutting an asymmetrical straight line. To eliminate this deviation, the iterative learning control method is introduced to obtain the optimal laser beam movement path. The fracture contour image is grabbed by a CCD camera after laser cutting completion. A new image processing system is proposed to detect the deviation between the desired cutting path and the actual fracture trajectory. The laser-movement path for the next trial can then be determined according to the iterative path revision algorithm. The actual fracture trajectory converging to the desired cutting path is assured after a few path revisions. The experimental materials used in these experiments are alumina ceramics and the laser source is CO₂ laser. The proposed system can achieve a machining precision of about 0.1 mm.     

现代数控刀具现状及发展趋势

数控机械加工技术的发展，促进了数控刀具材料及结构的发展。本文简介现代数控刀具的现状及发展趋势。     

Diagnosing unknown aberrations in an adaptive optics system by use of phase diversity

We outline a novel method for estimating a fixed aberration that is in the image path but not in the wave-front-sensor (WFS) path of an adaptive optics (AO) imaging system. We accomplish this through a nontraditional application of the Gonsalves [Proc. SPIE 207, 32 (1997)] least-squares phase-diversity technique, using an ensemble of images and WFS data. The diversity phases required for this technique are provided by the temporal differences in WFS residual phase measurements for different members of the ensemble. We demonstrate the technique by using actual observations from an operational AO system exhibiting such an aberration. An estimate of this aberration was obtained by the proposed algorithm that agrees reasonably well with the observed point-spread function.     

母线含非圆曲线的超声变幅杆精确加工的研究

介绍在普通数控车床上准确加工母线含非圆曲线的超声变幅杆的两种通用程序的编制方法及应用。方法一以等弦长划分待加工曲线决定节点,以平均曲率半径作为插补圆半径,以C语言编制出加工代码生成软件。方法二采用VB6编程,使用双圆弧法进行插补,伸缩步长法进行误差控制和决定节点,可设定并控制插补误差理论值,运行时生成的NC代码指令条数少,适应任何超声变幅杆的加工,界面友好易用。上述两程序在进行切削加工前,均可全程模拟加工过程。两软件经分别在GSK-928和G-CNC6135A(G)数控车床上应用,效果良好。而第一软件较完善。     

Diffusive Wave Spectroscopy of a random close packing of spheres

We are interested in the propagation of light in a random packing of dielectric spheres within the geometrical optics approximation. Numerical simulations are performed using a ray tracing algorithm. The effective refractive indexes and the transport mean free path are computed for different refractive indexes of spheres and intersticial media. The variations of the optical path length under small deformations of the spheres assembly are also computed and compared to the results of Diffusive Wave Spectroscopy experiments. Finally, we propose a measure of the transport mean free path and a Diffusive Wave Spectroscopy experiment on a packing of glass spheres. The results of those experiments agree with the predictions of this ray tracing approach.     

Non-Poissonian exciton populations in semiconductor nanocrystals via carrier multiplication

We analyze distributions of exciton populations in PbSe nanocrystal (NC) ensembles as a function of excitation wavelength. For photon energies that result in carrier multiplication, these distributions are non-Poissonian and are characterized by two dominant exciton multiplicities that are determined by the ratio of photon energy to NC energy gap. For certain photon energies, we produce photoexcited NC ensembles with a nearly pure single multiplicity that can be tuned from 1 to 7. This result can find applications ranging from lasing and nonlinear optics to photovoltaics and photocatalysis.