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The Complete Handbook of Camera Image Sensors
The practical reference for engineers, technicians, and serious photographers who need to select, evaluate, and maintain image sensors with confidence.
by Alumigogo Books
Chapter 1: Understanding Camera Image Sensors
A camera image sensor is the electronic component inside a digital camera that converts light into an electrical signal. That signal is then amplified, digitized, and processed to create the image file you see on your screen. It is, quite simply, the heart of any digital imaging system — a modern camera without a sensor is just a lens cap and a battery compartment. Every image you capture, every photo you edit, and every machine-vision decision you make relies on the physical characteristics of this single component.
To understand what a sensor actually does, it helps to think about its job in stages. First, it must collect light. Second, it must convert that light into a measurable electrical quantity. Third, it must organize that information in a spatial array that corresponds to the image being formed by the lens. The entire history of digital camera development, from the first crude CCDs of the 1970s to today's sophisticated back-side illuminated stacked sensors, is a story of improving one of these three steps.
The collection of light begins with the photodetector, which is typically a photodiode embedded in a silicon substrate. When a photon of sufficient energy strikes the silicon, it can excite an electron from the valence band into the conduction band, creating a free electron and a hole. This process is called the photoelectric effect, and it is the fundamental physics that makes digital imaging possible. The number of photoelectrons generated is directly proportional