剪切力模式近场扫描光学显微镜的恒幅反馈控制方法研究

剪切力模式近场扫描光学显微镜(Near-field Scanning Optical Microscopy,NSOM) 的音叉探针间距控制系统中,用相位反馈控制和检测剪切力,同时采用比例＋积分（PI）技术实现对音叉探针振幅的反馈控制,使探针振幅在扫描过程中保持为恒定值.用相位信号作为探针与样品间距控制信号,分别在无振幅反馈和有振幅反馈两种情况下,以不同速率扫描得到标准CD_RW光盘光栅的两组图像,并进行了比较分析.实验表明,恒振幅反馈电路的引入有助于提高探针系统的响应速度和灵敏度,改善所得图像的质量及分辨率.

Constant Amplitude Feedback Control in Near-field Scanning Optical Microscopy in Shear Force Mode

A method is described to control the amplitude of the tuning fork probe while scanning on the surface of the sample in the Near-field Scanning Optical Microscopy(NSOM).The phase signal is used as the signal of distance control signal between tip and sample in the shear-force detection mode.Meanwhile the PI feedback technique is introduced to feedback control both the amplitude and phase of the probe resonance,the amplitude and phase of the tuning fork probe keep a constant value while scanning imaging.The NSOM images of the standard CD_RW grating with amplitude feedback circuit and without amplitude feedback circuit in different scanning speeds are obtained,and the two sets of images are compared.The experiment results shows that the introduce of constant amplitude feedback circuit can increase the response of the tuning fork probe system,meanwhile can improve the quality and resolution of the images gained by shear-force SNOM with bi-feedback control system of amplitude and phase.