Over 20 indices developed as vegetation index and the most famous was the normalized difference vegetation index (NDVI), hence would also be used in this study for computation of VSWI. For MODIS data, NDVI can be calculated as:NDVI=��2?��1��2+��1(1)where ��1 and ��2 were reflectance in MODIS bands 1 and 2 respectively. Since MODIS used on-orbit calibration method for its data, implying that the calibration parameters would vary with times and channels, it was necessary to acquire the essential calibration parameters, scales an
Active pixel sensors (APS) in CMOS technology have recently gained a lot of interest. Many functionalities can be implemented at the pixel level, ranging from basic charge integration, amplification to pre-processing of the data. However, the fact that the pixel readout electronics shares the die area with the sensor elements may limit considerably the sensitivity, and also leads to the presence of dead areas (between the photodiodes) which is unacceptable for certain applications. The reduction of feature size in CMOS technology renders the problem more acute because the sensor area is further reduced and the increase in the number of the metal layers introduces difficulties for the coupling of light with the sensor.Vertical integration of hydrogenated amorphous silicon (a-Si:H) sensors on top of readout electronics is a promising solution to this problem. This concept has been pioneered by the University of Siegen [1] with the demonstration of this technology for several this website applications, especially for vision sensors with high sensitivity [2,3] or high dynamic range [4]. This integration concept is known as thin-film on ASIC (TFA), thin-film on CMOS (TFC), above IC (integrated circuit) or elevated diode technology (in the cases where a diode is used) and has attracted a large interest, not only for imaging application but also for particle detection, MEMS (micro electro-mechanical systems) or BioMEMS (biological MEMS) [5].For light detection, TFA technology offers several advantages compared to c-Si technology with embedded photodiodes:Maximization of sensitivity since the entire chip area may be dedicated to light collection.Separation between optimization of the photodiode and design of the CMOS circuit.Flexibility in the choice of the active material for the photodiode allowing the adjustment of the spectral sensitivity.Vertical integration of several photodiodes forming a multi-junction device or combination with other functional layers such as a scintillating layer for X-ray to light conversionThe typical structure of such a device is presented in Fig. 1.Figure 1.Schematic view of an array of sensors in TFA technology. In most cases, the CMOS circuit passivation layer is used as the insulation layer. The top metal layer of the CMOS chip is either used as the back electrode of the a Si:H diode layer or an additional …