Surface Plasmon resonance (SPR) technique is gradually growing as a research focus in optical area, which has been widely applied in many disciplines. The fiber-based SPR sensor, combining the advantages of fiber and SPR phenomenon, will lead to more tremendous application areas. The design and fabrication of different fiber SPR sensors are always be focuses of researchers in recent year, but the characteristic wavelength demodulation of the SPR sensor didn’t obtain enough attention. In this paper, the detection system for a fiber-based SPR sensor was presented first, and the detection mechanism of the refractive index sensing was obtained theoretically. Based on the theoretical simulation and analysis, the analytical expression of the all-phase low-pass filters was deduced, which is used for the de-noising of the original spectrum for the SPR sensing system, leading to resonance wavelength extraction only by calculating the derivative of the de-noised signal. So the resonance wavelength of the SPR sensor can be easily obtained by using this simple demodulation algorithm. Based on the realization of the system, the refractive index sensing of alcohol solution was carried out. And a good linear relationship between the refractive index of the solution and the characteristic wavelength of the SPR sensor can be obtained, with refractive index sensitivity and fitting error of 2048.5 nm/RIU and 5.69 nm respectively.
A spatial super-resolution method is proposed based on the multiplicative character of confocal microscope’s amplitude point-spread functions. The axial resolution can be greatly improved by introducing a shifted-focus phase filters in illumination part of a confocal microscope. However, this improvement is accompanied by a decrease of transversal resolution. Thus, a super-Gaussian phase filter is optimized to control the focal shift and transversal intensity distribution in a confocal microscope. Numerical simulation results indicate that the proposed method is useful to obtain a significant improvement in the optical sectioning capacity.
In order to obtain a high resolution image required for ultra-precision measurement of microstructural object, a new approach is proposed for 3D microstructures. It uses the modulation transfer function with defocus aberration based on the ambiguity function and stable phase principle to achieve an optical phase filter, and utilizes generalized a spheric phase optical element to encode defocus images, and uses deconvolution technology to recover the images. In comparison with conventional optical system, the phase filter used in the optical system can make focal spot smaller when measure object defocusing, eliminates the effect of the defocus aberration, and improves the defocused property. Numerical results indicate the designed phase filter can improve lateral resolution of optical system, and the axial resolution of the optical system is not affect by the filter and defocus aberration. For different defocus plate, the phase filter can make character of modulation transfer function of lateral direction uniform approximation.