A new subdivision technique for grating based on CMOS microscopic imaging

We propose a new subdivision technique directly subdividing the grating stripe by using complementary metal-oxide semiconductor (CMOS) microscopic imaging system combined with image processing. The corresponding optical system, subdivision principle, and image processing methods are illuminated. The relations of systemic resolution to subdivision number, grating period, magnifying power and tilt angle are theoretically discussed and experimentally checked on the Abbe comparator. The measurement precision for displacement of the proposed subdivision system is tested in the range of 5 mm and the maximum displacement error is less than 0.4μm. The factors contributing to the systemic error are also discussed.     

马兰黄土的应力-应变本构方程

依据马兰黄土的室内CU试验,运用土力学的相关理论,建议性地提出了马兰黄土的应力-应变本构方程。通过对不同围压下的试验结果(应变小于15%)与理论模型的拟合发现,二者吻合较好。另外,与以往的模型相比,本文的模型参数a和b只需通过一次常规三轴试验即可全部求得,具有参数少、容易确定的优点。     

Nonlinear effect of the structured light profilometry in the phase-shifting method and error correction

Digital structured light （SL） profilometry is increasingly used in three-dimensional （3D） measurement technology. However, the nonlinearity of the off-the-shelf projectors and cameras seriously reduces the measurement accuracy. In this paper, first, we review the nonlinear effects of the projector-camera system in the phase-shifting structured light depth measurement method. We show that high order harmonic wave components lead to phase error in the phase-shifting method. Then a practical method based on frequency domain filtering is proposed for nonlinear error reduction. By using this method, the nonlinear calibration of the SL system is not required. Moreover, both the nonlinear effects of the projector and the camera can be effectively reduced. The simulations and experiments have verified our nonlinear correction method.     

基于正弦相位编码的相机离焦标定

分析了光学系统离焦状态对基于正弦光栅的结构光相位的影响.基于正弦结构光相位与相机对焦状态无关的性质,提出了一种利用相移法正弦结构光编码显示面板对离焦相机进行标定的方法.使用Floyd-Steinberg Dithering算法消除了显示面板gamma变换带来的结构光相位计算误差.实现了相机在离焦状态下对标定物特征点的准确提取.标定结果重投影误差为0.17pixels.相机焦距的标定误差在0.39%以内.与传统方法相比提高了标定精度,为具有特殊成像范围的相机的标定提供了一种解决方案.     

Fabrication and characterization of two-dimensional pin-cushion position sensitive detectors

In this paper, the fabrication and testing results of a two-dimensional pin-cushion position sensitive detector (PSD) are presented. The obtained pin-cushion PSD with an 8 × 8 mm2 effective area presents a maximum spectral response of 0.5 mA/mW at 850-nm wavelength, a 12-nA dark current at 5-V reverse voltage, a reverse breakdown voltage of 50 V, a nonlinearity of 2.175%, and a spatial resolution of 10 μm. The spatial resolution is relatively low and the slight pin-cushion concave distortion is generated due to the incompletely satisfied relationship between sheet resistivity of the anode and the resistance per unit length.     

A new interpolating method based on the variation of spectra energy using CMOS array

A new interpolating method to enhance the resolution of gratings using complementary metal-oxide semiconductor (CMOS) according to the variation of some specified spectral light intensities during the motion of scale grating in a periodic separation is proposed. CMOS image sensor (pixel array 648×488) was also introduced as receiving device and its stability was verified experimentally. Many factors in the experiment were analyzed theoretically and contrasted with experiment. The advantages of this novel method were featured by CMOS and the specified spectral variation of the energy distribution was discussed.     

介质平面波导TE0模衍射场的光束参量

对于傍轴光束，提出了介质平面波导衍射场的近场模场半宽度、远场发散角半宽度和光束传输因子M^2等光束参量之间满足简单的关系式，三个光束参量均可直接由波导模式场分布精确计算，或由可实际精确测量的远场衍射频谱分布精确计算。M^2因子的计算公式可表述为以二阶矩和微分算子定义的近场模场半宽度的比值，或以二阶矩和微分算子定义的远场发散角半宽度的比值。最后推导出介质平面波导TE0模衍射场光束参量的解析函数和光束参量的范围。     

锥形光栅衍射特性分析

针对光学绝对式编码器的分辨率和尺寸之间的矛盾,自行设计了一种锥形光栅进行高位细分.以夫琅和费衍射理论为基础,分析了锥形光栅的光学衍射特性,初步推导了利用锥形光栅实现光学细分的基本原理,并通过实验验证了上述的理论分析结果.     

基于QLF原理的龋齿探测方法中光学参量变化分析

通过建立完整的病变牙齿模型和龋齿病变程度判据,利用蒙特卡罗仿真算法编程,完整模拟了牙齿组织中荧光的激发和传输过程,探讨了牙齿组织病变程度引起的光学参量变化与QLF荧光分布的关系.同时,利用Tracepro软件的荧光仿真功能验证了该过程的合理性.结果表明:随着龋齿部分病变程度增大,散射系数增大,吸收系数和荧光量子效率减小,健康组织和病变组织荧光分布差异增大.     

基于QLF原理的龋齿探测方法中光学参量变化分析

通过建立完整的病变牙齿模型和龋齿病变程度判据,利用蒙特卡罗仿真算法编程,完整模拟了牙齿组织中荧光的激发和传输过程,探讨了牙齿组织病变程度引起的光学参量变化与QLF荧光分布的关系.同时,利用Tracepro软件的荧光仿真功能验证了该过程的合理性.结果表明：随着龋齿部分病变程度增大,散射系数增大,吸收系数和荧光量子效率减小,健康组织和病变组织荧光分布差异增大.