This paper proposed an imaging system based on Fairchild's low-illumination SCMOS detector CIS2521F and ALTERA's Cyclone IV E EP4CE40U19I7N FPGA, which has the characteristics of high sensitivity and low noise. Based on its electronic parameters, a real time imaging system is developed. The hardware system structure of the imaging system mainly consists of a SCMOS image sensor, a programmable gate array (FPGA), a driving circuit of a combination of DDR2 and a Camera Link transfer circuit. The software system consists of SCMOS initialization module, automatic exposure control module and image enhancement module, which has the capabilities of automatic exposure control and low-light image enhancement. Automatic exposure control module is proposed based on the image gray statistical algorithm. It is used to choose the best exposure time in the complex light situation. The image enhancement module is proposed based on an improved Dual platform histogram enhancement algorithm. The improved histogram equalization algorithm can avoid many image issues, such as over-enhancement, uniform area noise amplification, bleaching etc. The details of the image are preserved well and the signal to noise ratio of the image is improved by this method. The imaging results show that the system is working normally. And the imaging quality meets the expected requirements.
Switchable multiwavelength fiber laser outputs with a wide tuning range are experimentally observed in an ultralong cavity. Because of the long spooled single-mode fiber and filter effect of the cavity, multiwavelength lasers with the spacing of ~14.5 nm are obtained. The proposed fiber laser has the capacity of simultaneously emitting the three wavelengths. By means of adjusting the polarization controllers, the arbitrary single- and dual-wavelength operations are achieved in our laser.
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