In this study, we described the scanning area limitation (SAL) speciality in laser flying marking and defined maximum markable time and maximum marking offset (MMO) for analyzing the effect of SAL on flying marking process. We presented maximum flying velocity (MFV) to evaluate the performance of a laser marking system and investigate the factors, including the the length of marking graphics in the moving direction and the marking order of graphics objects, which will impact the maximum flying velocity very much. Transverse and vertical directions of graphics entering into the scanning area and three object scanning path algorithms, the all-entered-marking, first-entering-first-marking (FEFM), and rowed-FEFM were analyzed and compared, and MMO and MFV were calculated using these algorithms. Experimental MFV results with different algorithms satisfied theoretical calculations very well, and it was shown that there is a best MFV performance when using the FEFM scanning path algorithm in the transverse moving direction.
A laser flying marking system with a galvanometer scanner could be widely used as a workhorse because the moving speed of product on the workline would not be affected while being marked. A laser flying marking system, with high-speed galvanometer scanners, was set up. Two kinds of marking effects, vector style and matrix style, were realized in the system. Different motion-tracing methods, including a closed-loop feedback tracing mode and an open-loop computing tracing mode, were studied and utilized in the control software. Experimental results show that the system using the closed-loop feedback motion-tracing method has more adaptability for variable-speed applications.
Infrared clutter rejection is especially crucial and very difficulty when the point targets have complicated background such as cloud, ocean waves irradiated by sunlight. In this letter, we introduce a new algorithm of point targets detection based on wavelet. The modulus maximum of adjacent positive-negative in fine scale has been proved to be correspondence to point-like targets. So the strong clutter can be highly suppressed in this way. Experiment results show the method has good performances.
A scenario using cascade long-period fiber gratings to flatten the gain spectrum of the Erbium Doped Fiber Amplifier (EDFA) is presented. Long-period fiber grating can act as a kind of wavelength selective loss device, in which the guided mode is coupled with forward transmit cladding modes. Cladding mode resonance in long period fiber grating is analyzed and cladding mode fields are simplified by using coupled mode theory. The loss spectrum formula versus propagation constant and refractive index fluctuation is obtained. Four long-period fiber gratings based on standard single mode fiber are designed for the typical EDFA's gain spectrum by using more accurate transmission spectrum formula. The resulted fiber gratings chain is used to flatten the broadband gain spectrum. The computer simulation result is satisfying.
Many conventional methods to detect propagation losses in optical waveguides, such as Cut-Back Method and Prism-Sliding Method, are either destructive or inconvenient. Here we demonstrated a new method -- CCD camera photographing method. A CCD camera was used to take digital photographs of the light streak in the waveguides and the scattered-light intensity distribution is recorded. After fitting the intensity distribution into an exponential attenuate curve, the propagation loss finally can be calculated from the attenuation coefficient of the curve. Compared with other detecting methods, it is more convenient and accurate. In our experiment, samples of polymer waveguides with propagation losses less than 0.5 dB/cm were fabricated.