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Image Detector ArrayThe image detector array is a two-dimensional grid of pixels. The number of pixels on the grid is called the resolution of the image sensor. Bigshot's sensor has a resolution of 1.9 megapixels, which means that it has about 1.9 million pixels (arranged in a grid of 1200 rows and 1600 columns). Figure 2 shows the structure of an individual pixel.
Although each pixel contains a significant amount of electronics, it is usually no larger than a few microns (thousandths of a millimeter). The pixel's top layer (the light-blue surface in Figure 2) is usually made of silicon and is sensitive to visible light. When light strikes the silicon, some of its energy is transferred to the electrons inside the silicon's atoms. If the energy is great enough, the electrons are set free, a phenomenon called the photoelectric effect [1]. The freed electrons are collected in a bucket-like region known as the potential well. The number of freed electrons, and hence the amount of charge that builds up in the potential well, depends on how much light falls on the pixel. Next, an electronic circuit measures the voltage of the potential well. In the case of CMOS (Complementary Metal Oxide Semiconductor, pronounced "see moss") image sensors, each pixel has its own circuit to perform the charge-to-voltage conversion [2]. The circuit blocks incoming light, so a microlens is used to direct the light away from the circuit. Alternatively, CCD (Charged Coupled Devices) image sensors use a single circuit for all pixels, and the conversion is done one pixel at a time [2]. Both CMOS and CCD technologies have their merits and disadvantages [2]. Bigshot's sensor is a CMOS sensor.
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