Optical Computed Tomography Apparatus using Optical Nonlinear Effect

利用光学非线性效应的光学计算机断层扫描设备

基本信息

批准号：
06555016
负责人：
HORINAKA Hiromichi
金额：
$ 6.46万
依托单位：
Osaka Prefecture University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Developmental Scientific Research (B)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

项目摘要

1. Only coherent component in the light transmitted through a scattering medium produces the second harmonic light by mixing with pump beam in a nonlinear crystal. Before the experiment of optical mixing, the light traveling along the straight line in the scattering medium was extracted by the method utilizing the coherence of light (light polarization). The transmitted light intensity was measured as a function of the concentration of the scattering medium. The follr level of the transmitted light due to diffused light was significantly suppressed by detecting photons preserving initial polarization.2. The light pulse (2ps) from a mode-locked Ti : sapphire laser was divided into a pump beam and a probe beam. The probe beam transmitted through a scattering medium and the pump beam were mixed in BBO crystal. The peak intensity and the correlation width of the second harmonic light pulse was measured as a function of the concentration of the model scattering medium. The correlation width did not depend on the concentration of the scattering medium. The peak intensity linearly changed with the concentration of the scattering medium on the logarithmic scale as low as -85dB.These results showed that the light component traveling nearly along the straight line in the scattering medium was extracted by the optical mixing.3. The optical components used for the primary experiment were assembled on a board. The rotationtranslation stage was attached on the board to take the projection data of the sample from different directions. As a mode-locked YVO4 laser with sufficient peak intensity was not able to be developed, a mode-locked Ti : sapphire laser was used as a light source. The projection data of the absorbers in the scattering medium were taken by this apparatus. The clear CT image of absorbers was reconstructed from the projection data.

1. 通过散射介质传输的光中只有相干分量通过与非线性晶体中的泵浦光束混合产生二次谐波光。在进行光学混频实验之前，利用光的相干性（光偏振）的方法提取在散射介质中沿直线传播的光。测量透射光强度作为散射介质浓度的函数。通过检测保持初始偏振的光子，显着抑制了由漫射光引起的透射光的偏振水平。2．来自锁模钛宝石激光器的光脉冲（2ps）被分为泵浦光束和探测光束。透过散射介质的探测光束和泵浦光束在 BBO 晶体中混合。测量二次谐波光脉冲的峰值强度和相关宽度作为模型散射介质浓度的函数。相关宽度不依赖于散射介质的浓度。峰强度随散射介质浓度呈对数线性变化，低至-85dB。结果表明，光混频提取了散射介质中近乎直线传播的光分量。 3．用于主要实验的光学元件组装在一块板上。将旋转平移台安装在板上，从不同方向获取样品的投影数据。由于无法开发出具有足够峰值强度的锁模YVO4激光器，因此使用锁模Ti：蓝宝石激光器作为光源。吸收体在散射介质中的投影数据是由该装置获取的。根据投影数据重建吸收体的清晰 CT 图像。