离焦量对1Cr17Ni2薄钢板激光焊接接头组织与性能的影响

利用YAG脉冲激光焊接系统对1mm厚的1Cr17Ni2不锈钢薄板进行对接焊接试验,通过焊缝组织分析、拉伸测试和显微硬度测试,研究了离焦量对焊接接头组织与性能的影响。结果表明:采用激光对1Cr17Ni2薄钢板进行对接焊后,焊接接头出现了组织分区,母材区组织主要是铁素体和马氏体,热影响区组织为板条马氏体组织和少量呈带状分布的δ铁素体,而焊缝区组织则主要以马氏体为主;随着离焦量增加,焊缝熔深逐渐减小,熔宽先增大后减小,焊缝处的马氏体含量逐渐减少,接头的抗拉强度先增大后减小;焊缝区的硬度最大,母材区的硬度最小,热影响区的硬度介于两者之间;焊缝区的整体硬度随着离焦量的增大而减小;当离焦量为-5.5mm时,热影响区中马氏体板条束群细小均匀,焊接成形质量好,接头的拉伸性能优良。     

波束扫描反射阵列天线偏焦特性

针对波束扫描反射阵列天线在大角度扫描时增益下降及方向图恶化等问题,提出通过馈源偏焦来改善反射阵列天线的扫描性能。采用方形贴片结构设计了一款工作在X频段的反射阵列天线。研究馈源在15°,30°,45°扫描角的纵向偏焦以及10°,20°和30°扫描角的横向偏焦对波束扫描反射阵列天线性能的影响。测试结果显示,在扫描角度较小时,横向偏焦引起波束指向的改变,波束宽度变化不大。减小馈源纵向偏焦尺寸,旁瓣电平减小,中心频率处的增益提高,尤其是在较大的扫描角度时效果更加明显,有利于提高波束扫描反射阵列天线的大角度扫描能力。     

Global shape reconstruction of nano grid with singly fixed camera

Depth from defocus(DFD),as a typical shape reconstruction method,has been widely researched in most recent years.However,all the existing DFD algorithms require at least two defocused images with different camera parameters.Unfortunately,in micro/nano manipulation,any change on visual sensor's parameters is absolutely forbidden.Therefore,a novel DFD method to reconstruct the shape of a nano grid on micro/nano scale is researched in this paper.First,the blurring imaging model is constructed with the relative...     

波前编码成像系统的像差抑制特性分析

为了进一步研究波前编码技术对光学系统其它像差影响,基于像差衍射理论,通过数值模拟的方法系统分析波前编码成像系统中各种初级像差的传递特性。波前编码成像系统除了具有很好的离焦像差抑制能力外,对球差、慧差、像散、场曲等初级像差也有很好的抑制作用。     

基于编码孔径的折反射散焦模糊图像复原

360度折反射成像系统由于其曲面反射的成像特点,获得的全向图像会不可避免地产生散焦模糊问题,使得全向图像的应用受到限制。针对全向图像成像过程中的散焦模糊问题,首先通过分析折反射系统中入射光线和图像模糊的关系,建立全向图像散焦数学模型;然后利用编码孔径技术估计出图像中各个位置的模糊程度;最后通过反卷积算法复原图像。通过该方法,可以很好地消除全向图像的散焦模糊,获得全聚焦的清晰全向图像。获得的全聚焦全向图像在全向智能视频监控、战场环境全向智能感知以及机器人全向视觉等领域具有较大应用价值。     

Defocus deblurring for catadioptric omnidirectional imaging based on spatially invariant point spread function

The problem of catadioptric omnidirectional imaging defocus blur, which is caused by lens aperture and mirror curvature, becomes more severe when high resolution sensors and large apertures are applied. In order to overcome this problem, a novel method based on computational photography is proposed. Firstly, the defocus blur of catadioptric omnidirectional imaging is analyzed to calculate the point spread function for different scene points. Then, the defocus blur kernel of omnidirectional image is confirmed to be spatially invariant when rotating the focus ring of camera lens during an image’s integration time. Lastly, the deconvolution algorithm using prior sparse derivatives is applied to obtain all-focused/sharp omnidirectional images. Experimental results demonstrate that the proposed method is effective for omnidirectional image deblurring and can be applied to most existing catadioptric omnidirectional imaging systems.     

Depth recovery and refinement from a single image using defocus cues

We present a technique to recover and refine the depth map from a single image captured by a conventional camera in this paper. Our method builds on the universal imaging principle: only scene at the focus distance will converge to a single sharp point on imaging sensor but other scene will yield different blur effects varying with its distance from the camera lens. We first estimate depth values at edge locations via spectrum contrast and then recover the full depth map using a depth matting optimization method. Due to the fact that some blur textures such as soft shadows or blur patterns will produce ambiguity results during the procedure of depth estimation, we use a total variation-based image smoothing method to smooth the original image, a smoothed image with detailed texture being suppressed can be generated. Taking this smoothed image as reference image, a guided filter is used to refine the final depth map.     

猫眼终端回波闪烁效应分析

利用Rytov近似和物理光学传输矩阵法,研究了猫眼光学系统离焦量对逆向通信系统中猫眼终端回波闪烁效应的影响,得到了水平传输时高斯波束在接收平面的闪烁指数的表达式,通过数值仿真实验分析了猫眼光学系统的离焦量对接收平面光强闪烁指数的影响.结果表明,无论湍流和传输距离如何改变,总是存在一定的离焦量使得闪烁指数最小;离焦量增大时闪烁指数总体呈现先减小后增大的趋势,且随着距离和湍流的增大闪烁指数也增大.     

双孔离焦成像法齿条测量研究

提出一种基于双孔离焦成像的三维测量方法。通过在成像光路中加入掩膜版,使离焦物体通过掩膜版后在CCD上成双像,根据双像的相对位置,获得成像物体的空间三维位置。在分析相机成像模型的基础上,推导了离焦成像三维反演方法模型,分析了结构参数对测量精度的影响。搭建了三维测量仪器,对齿条进行测量实验,实验结果表明,本文方法能实现齿条等三维物体的快速,非接触测量,具有较高的测量精度,误差小于2μm。