Photoacoustic imaging is an imaging technology which combines the advantages of high-resolution optical imaging and deep detection depth of acoustic imaging. Photoacoustic imaging combined with hysteroscopy may be a new diagnostic technique for endometrial cancer. However, the energy loss after pulsed laser passing through the hysteroscope is very large. Therefore, the energy of pulsed laser after hysteroscopy based on photoacoustic imaging is worth further discussion. A coupling Program of pulsed laser and hysteroscope based on the optical path of pulsed laser and hysteroscope was designed in this paper. The Program was optimized by ZEMAX simulation, and then the optimal effect of pulsed laser observation through hysteroscopy was verified by phantom experiment. The results show that the pulsed laser can obtain better photoacoustic signals after passing through our coupling module. This method is expected to be applied to the detection of endometrial diseases in clinic.
为了研究基于激光回馈的偏振跳变效应与相位延迟间的内在联系,采用微片Nd∶YAG激光器(中心波长1064 nm)为光源,回馈腔内置两个相对旋转的λ/4 波片改变相位延迟,在调谐回馈腔长的过程中研究了激光器的光强输出和偏振态变化.结果表明,随着回馈腔内相位延迟增大,偏振跳变点的凹陷逐渐加深,两个偏振态的光强调制波形宽度趋于相同;当回馈腔中相位延迟为 90°时,两正交偏振态在一个强度调制周期内持续时间相同,每一次偏振跳变对应回馈腔长改变λ/4.此不同相位延迟下偏振跳变点的变化规律,为 1064 nm波长下的波片相位延迟测量提供了潜在方法,同时相位延迟对激光器输出光强曲线的整形、为激光回馈条纹(自混合干涉条纹)的光学细分提供了依据.
In order to solve the problems of artifacts and unreal details when process low-resolution blurred images using image enhancement methods, a low-resolution blurred image enhancement algorithm based on deep dense residual generative adversarial network（DDR GAN） was used to achieve effective enhancement of low-quality images. Firstly, an end-to-end generative adversarial network framework was constructed; further, a deep dense residual latent feature encoding architecture was designed to improve the deep semantic feature representation of the input image and enhance the image generation efficiency; finally, the loss function was reconstructed and the perceptual loss was added to guide the model to learn to generate realistic images. The comparative experimental results show that compared with the current state-of-the-art enhanced super-resolution GAN（ESR GAN） and DeBlur GAN-V2 algorithms, the images generated by DDR GAN are visually better, with higher definition and richer image detail. In terms of objective evaluation indicators, compared with ESR GAN and DeBlur GAN-V2, the peak signal-to-noise ratio was improved by 1.7072 dB and 1.1683 dB through DDR GAN, respectively, and the structural similarity by 0.0783 and 0.0713, respectively. This algorithm is helpful for the restoration and enhancement of low-resolution blurred images.
为了研究自相似脉冲在Mach-Zehnder干涉仪的压缩特性,采用非线性薛定谔方程对自相似脉冲的演化和压缩进行了模拟,分析了基于级联单模光纤的Mach-Zehnder干涉仪的光纤参数对脉冲压缩的影响.结果表明,在不考虑高阶色散的情况下,当上臂的两种单模光纤长度分别为 8.16 m和 2.16 m、下臂的单模光纤长度为 8.16 m时,获得半峰全宽为 27.85 fs、峰值功率为 1860.59 W、基座能量比例为 10.241%的最佳压缩脉冲;考虑高阶色散时,脉冲在单模光纤中传输呈现出峰值功率增大、基座增大的现象,且脉冲右移不利于输出基座较小的压缩脉冲;当 3 阶色散系数小于0.001 ps3/km时,利用Mach-Zehnder干涉仪来压缩能获得质量较好的飞秒脉冲.该研究结果对于自相似脉冲的压缩研究具有一定的参考价值.
为了提升调频连续波激光雷达调制带宽、从而提高距离分辨率,采用基于双平行Mach-Zehnder调制器的外调制方式,结合无光滤波器的微波光子倍频技术,通过 1 GHz的射频源实现 8 GHz的宽带射频调制信号,并利用搭建的模型研究了微波光子倍频子系统中消光比、调制系数和移相器相位偏移 3 个参数的变化对调频连续波激光雷达系统性能的影响.结果表明,大部分商用调制器的消光比可以满足使用需求,调制系数在 2.385～2.425 范围内或电移相器误差不大于 1.3°时,该激光雷达探测信号峰的功率抑制比可以保持在 20 dB以上.此研究结果为微波光子倍频技术在调频连续波激光雷达中的应用提供了理论支持,对工程实现有一定的参考意义.
