Lecture

CMOS Cameras: Shutter Mechanisms and Noise Sources

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Description

This lecture discusses the properties of 3D Active Pixel Sensors in CMOS cameras, focusing on the rolling shutter effect and its implications for image capture. The instructor explains how the rolling shutter records each line of an image at slightly different times, leading to potential image deformation. Solutions to this issue, such as using mechanical shutters for instantaneous snapshots, are presented. The lecture then transitions to an analysis of noise sources in CMOS cameras, including photon noise, dark current noise, and reset noise. The instructor elaborates on the significance of correlated double sampling and the impact of amplifier noise on image quality. The discussion includes the advantages of using pinned photodiodes in CMOS image sensors to minimize dark current and reset noise. The lecture concludes with a comparison of standard photodiodes and the technology used in CMOS image sensors, emphasizing the importance of noise management in achieving high-quality imaging.

Official source

Ontological neighbourhood

Information engineering

Signal processing: Digital image processing

Related concepts (32)

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.

Active-pixel sensor

An active-pixel sensor (APS) is an , which was invented by Peter J.W. Noble in 1968, where each pixel sensor unit cell has a photodetector (typically a pinned photodiode) and one or more active transistors. In a metal–oxide–semiconductor (MOS) active-pixel sensor, MOS field-effect transistors (MOSFETs) are used as amplifiers. There are different types of APS, including the early NMOS APS and the now much more common complementary MOS (CMOS) APS, also known as the CMOS sensor.

Image noise

Image noise is random variation of brightness or color information in s, and is usually an aspect of electronic noise. It can be produced by the and circuitry of a or digital camera. Image noise can also originate in film grain and in the unavoidable shot noise of an ideal photon detector. Image noise is an undesirable by-product of image capture that obscures the desired information. Typically the term “image noise” is used to refer to noise in 2D images, not 3D images.

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.

Pink noise

Pink noise, noise or fractal noise is a signal or process with a frequency spectrum such that the power spectral density (power per frequency interval) is inversely proportional to the frequency of the signal. In pink noise, each octave interval (halving or doubling in frequency) carries an equal amount of noise energy. Pink noise sounds like a waterfall. It is often used to tune loudspeaker systems in professional audio. Pink noise is one of the most commonly observed signals in biological systems.

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