Gabor zone plate (GZP) is typical amplitude-type diffractive lenses for high-resolution imaging. Compared with Fresnel zone plates (FZP), GZP can suppress all higher-order foci and shows better focusing performance. However, the focusing efficiency of GZP is very low and the cosine variation of its transmittance is difficult to satisfy. In order to improve these disadvantages, many kinds of improved Gabor zone plates are designed. However, the focusing efficiency of these Gabor zone plates are ~10%, which is still too low. A phase-type diffractive lens based on the Gabor zone plate is designed to improve the focusing efficiency of GZP, in which the radial distribution of microstructure varies in a cosine pattern. Simulation results show that the focusing efficiency of the Gabor-type diffractive lens (GDL) can reach ~22%, which is much higher than that of GZP. In addition, we also analyze the effect of errors of laser direct writing on the focusing efficiency of GDL and Fresnel-type diffractive lens (FDL). The results show that the focusing efficiency of GDL shows higher tolerance for the error of laser direct writing than that of FDL.
In this paper, a micro-projection display with telecentric beam path in image space is designed. The device consists of a 0.26-inch liquid crystal on silicon (LCOS), a polarizing beam splitting cube and a hybrid refractive-diffractive eyepiece. The refractive-diffractive eyepiece has a focal length of 9.16 mm, a full field of view of 40° and a spectral bandwidth of 422~632 nm. The eyepiece is optimized by the wide-angle eyepiece, which consists of four optical lenses. The designed hybrid refractive-diffractive micro-projection display system has good projection effect while using a small number of lenses in a simple structure. This provides a reference for the future development of lightweight micro-projection systems.
The parallel wire fine line control system is mainly used for the adjustment of the distance between the two electrode wires and the parallel control during the fabrication of the miniature thermocouple. It mainly adopts precision electronic control and computer vision precision micro-measurement technology to ensure the adjustment and stability of the two-electrode wire spacing parameters during thermoforming. Hanging 17μm-60μm wire on the device, tightening the suspension wire by controlling the two-phase stepping motor, adjusting the five-phase stepping motor to adjust the parallel wire spacing, collecting the wire image in real time, automatically interpreting the wire spacing parameter by using a fast algorithm, and interpreting the wire The result output is displayed.
In this paper, the radial refractive index change of the grin lens is measured based on the principle of Mach-Zehnder interference. Using an image sensor to obtain experimentally detected images, the computer-derived interference pattern is subjected to grayscale stretching and filtering, and then the center position of the interference ring and the distance between the interference rings are determined to obtain the refraction of the grin lens. The rate changes. Through experiments, the actual samples of different thicknesses were tested, and the measurement accuracy can reach 10-4.
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