Lecture

CCD Cameras: Dark Current and Noise Analysis

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Description

This lecture discusses the various noise sources in CCD cameras, focusing on dark current and its implications. It begins by identifying different types of noise, including photon shot noise and dark current shot noise. The instructor explains how dark current arises from thermal generation of minority carriers and its dependence on temperature, noting that it can double with every 7-8 degree increase. The lecture provides numerical examples of dark current densities in various technologies, highlighting the importance of minimizing dark current for improved performance. The discussion includes the mechanisms of dark current generation, such as band-to-band generation and trap-assisted thermal generation, emphasizing the need for high-quality materials to reduce noise. The instructor also introduces the concept of pinned phase surface inversion to mitigate dark current effects. The lecture concludes with insights into advanced designs that achieve low dark current levels, which are crucial for applications like astrophotography, where long exposure times are necessary.

Official source

Ontological neighbourhood

Information engineering

Signal processing: Digital image processing

Related concepts (32)

Charge-coupled device

A charge-coupled device (CCD) is an integrated circuit containing an array of linked, or coupled, capacitors. Under the control of an external circuit, each capacitor can transfer its electric charge to a neighboring capacitor. CCD sensors are a major technology used in digital imaging. In a CCD , pixels are represented by p-doped metal–oxide–semiconductor (MOS) capacitors.

Image sensor

An image sensor or imager is a sensor that detects and conveys information used to form an . It does so by converting the variable attenuation of light waves (as they pass through or reflect off objects) into signals, small bursts of current that convey the information. The waves can be light or other electromagnetic radiation. Image sensors are used in electronic imaging devices of both analog and digital types, which include digital cameras, camera modules, camera phones, optical mouse devices, medical imaging equipment, night vision equipment such as thermal imaging devices, radar, sonar, and others.

Noise (electronics)

In electronics, noise is an unwanted disturbance in an electrical signal. Noise generated by electronic devices varies greatly as it is produced by several different effects. In particular, noise is inherent in physics and central to thermodynamics. Any conductor with electrical resistance will generate thermal noise inherently. The final elimination of thermal noise in electronics can only be achieved cryogenically, and even then quantum noise would remain inherent. Electronic noise is a common component of noise in signal processing.

Shot noise

Shot noise or Poisson noise is a type of noise which can be modeled by a Poisson process. In electronics shot noise originates from the discrete nature of electric charge. Shot noise also occurs in photon counting in optical devices, where shot noise is associated with the particle nature of light. In a statistical experiment such as tossing a fair coin and counting the occurrences of heads and tails, the numbers of heads and tails after many throws will differ by only a tiny percentage, while after only a few throws outcomes with a significant excess of heads over tails or vice versa are common; if an experiment with a few throws is repeated over and over, the outcomes will fluctuate a lot.

Johnson–Nyquist noise

Johnson–Nyquist noise (thermal noise, Johnson noise, or Nyquist noise) is the electronic noise generated by the thermal agitation of the charge carriers (usually the electrons) inside an electrical conductor at equilibrium, which happens regardless of any applied voltage. Thermal noise is present in all electrical circuits, and in sensitive electronic equipment (such as radio receivers) can drown out weak signals, and can be the limiting factor on sensitivity of electrical measuring instruments.

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