Wide dynamic cameras are widely used due to their excellent details capture ability in high contrast environments. This paper designed a hand-held wide dynamic camera with the NSC1105 image sensor. This camera is based on FPGA hardware platform for image acquisition, data conversion, image processing and OLED display. The miniaturized design realizes the hand-held of the camera. The experimental result shows that the hand-held wide dynamic camera can clearly distinguish the target in strong contrast environment, with the effective resolution of 1280*1024@52fps, and the detailed information collection ability is excellent.
Based on the study of working principle and making process of 4-transistor Backside-illuminated CMOS (4T BSI-CMOS), Signal-to-noise ratio (SNR) model are established and quantitative calculating formula is derived. In addition, factors of influencing SNR are analyzed. Two methods are presented to enhance the SNR, the one is optimizing structure of 4T BSI-CMOS image sensor to strengthen the signal and the other one is correlated double sampling to decrease fixed pattern noise (FPN). These results serve as useful guidelines to enhance the SNR of 4T BSI-CMOS and improve the image quality.
The photocurrent attenuation of GaAs photocathode within one hour after activation under three different vacuum pressure (5×10-9Pa, 5×10-8Pa, 5×10-7Pa) were recorded by automatically activated monitor. The results show that: the photocurrent quickly descend in the beginning and then descend linearly at a low slope; the amplitude of the quickly descending area were 10%, 14.74% and 36%separately, with the respective slope of the linear descending area were -0.00653, -0.01132and -0.02. Three samples’ gas components of H2, CH4, CO, H2O, O2, CO2 etc under the same vacuum pressure (5×10-8Pa)during photocurrent attenuation were collected by quadrupole mass spectrometer. By comparing the gas components content and the attenuation law of the photocurrent, it has been found that H2O and H2 had a greater impact on the stability of GaAs photocathode in the ultra-high vacuum environment and H2O was the predominant effect. This paper has important guiding significance and reference value in studying the stability of GaAs photocathode and the improvement of semiconductor photocathode process.
The GaAs photocathode has widely been used in optoelectronic devices such as image intensifiers, photomultiplier tubes, but these devices is inevitable to withstand a variety of mechanical vibration. In order to study the mechanical vibration impact on the photoemission performance of GaAs photocathode, GaAs photocathode image intensifier is researched in this paper. The spectral response of the GaAs photocathode before and after 5~55Hz scan frequency, 14Hz, 33Hz, 52Hz stay frequency, 5～60Hz scan frequency mechanical vibration respectively was tested, then the parameter of photocathode was calculated by MATLAB software according to quantum efficiency formula, the quantum efficiency curve were fitted. The results show that surface escape probability is increased after photocathode is subjected to mechanical vibration, so that its photoemission performance will be improved. We think this phenomenon is due to the GaAs photocathode surface Cs-O reconstruction. This finding provided a new method to enhance the photoemission performance of photocathode.
In this article, in order to accurately measure the spectral transmittance of imaging lens used in InGaAs imaging apparatus, a simple device, which spectrum ranges from 400 nanometers to 2000 nanometers, based on double grating monochromator and self-collimating has been founded by using stable shortwave infrared radiant source, accurate double grating monochromator and telescope, stable silicon detector and cooled HgCdTe infrared detector. An imaging lens whose spectral transmittance has been known is measured on it. Comparing the test results to known data provided by manufacture, it is shown that the testing device founded in this article is competent to measure spectral transmittance of shortwave infrared imaging lens and which max relative deviation is no more than ±2.5%. It is worthwhile for selecting InGaAs image intensifier assembly and evaluating the quality of shortwave infrared imaging lens.