Advanced

Automatic exposure control in network video cameras

Hydén, Hans and Wilhelmsson, Per (2011) In MSc Theses
Department of Automatic Control
Abstract
The overall objective of this study is to describe, analyse and suggest improvements on existing automatic exposure control systems in selected network video cameras. Since an image sensor has a limited dynamic range compared to a real scene, it is necessary to automatically control the exposure level and thus adapt to the amount of light in the scene. This can be done by adjusting parameters such as exposure time, gain and variable aperture in an automatic control loop. The two cameras in this study run different implementations of such a control loop and the topic of this study is to test their performance, to review their implementation of automatic exposure control, to comment on their implementation from a theoretical stand point, and... (More)
The overall objective of this study is to describe, analyse and suggest improvements on existing automatic exposure control systems in selected network video cameras. Since an image sensor has a limited dynamic range compared to a real scene, it is necessary to automatically control the exposure level and thus adapt to the amount of light in the scene. This can be done by adjusting parameters such as exposure time, gain and variable aperture in an automatic control loop. The two cameras in this study run different implementations of such a control loop and the topic of this study is to test their performance, to review their implementation of automatic exposure control, to comment on their implementation from a theoretical stand point, and to suggest improvements. The most focus has been correction of integrator function or adding of integrator functionality to the controllers to remove steady state errors. Integrator windup was solved for two cases. Some other minor bugs giving unwanted behavior such ass finite word length in the integrators. Also improving gain scheduling and correction of clamping of signals are suggested. A suggestion for smear control improvement is to use feed forward the changes when changes are needed to exposure, this enables to control faster and still limit the impact on the picture quality. (Less)
Please use this url to cite or link to this publication:
author
Hydén, Hans and Wilhelmsson, Per
supervisor
organization
year
type
H3 - Professional qualifications (4 Years - )
subject
publication/series
MSc Theses
report number
TFRT-5879
ISSN
0280-5316
language
English
id
8847385
date added to LUP
2016-03-16 12:21:26
date last changed
2016-03-16 12:21:26
@misc{8847385,
  abstract     = {The overall objective of this study is to describe, analyse and suggest improvements on existing automatic exposure control systems in selected network video cameras. Since an image sensor has a limited dynamic range compared to a real scene, it is necessary to automatically control the exposure level and thus adapt to the amount of light in the scene. This can be done by adjusting parameters such as exposure time, gain and variable aperture in an automatic control loop. The two cameras in this study run different implementations of such a control loop and the topic of this study is to test their performance, to review their implementation of automatic exposure control, to comment on their implementation from a theoretical stand point, and to suggest improvements. The most focus has been correction of integrator function or adding of integrator functionality to the controllers to remove steady state errors. Integrator windup was solved for two cases. Some other minor bugs giving unwanted behavior such ass finite word length in the integrators. Also improving gain scheduling and correction of clamping of signals are suggested. A suggestion for smear control improvement is to use feed forward the changes when changes are needed to exposure, this enables to control faster and still limit the impact on the picture quality.},
  author       = {Hydén, Hans and Wilhelmsson, Per},
  issn         = {0280-5316},
  language     = {eng},
  note         = {Student Paper},
  series       = {MSc Theses},
  title        = {Automatic exposure control in network video cameras},
  year         = {2011},
}