Defog Image Processing

Defog Image Processing
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Defog Image Processing
Introduction
Expectations for a camera’s performance, no matter the application, are that it must work and provide clear usable
images, regardless of any environmental or mechanical challenges the camera is exposed to.
These performance expectations have, and always will, drive technology solutions to compensate for difficult
conditions and external challenges. Some of the more notable performance challenges where technology has made
significant improvements are:
• Poor lighting - Day/Night Filtering, Increased Sensor Sensitivity, Supplemental Illumination
• Difficult lighting scenarios – Wide Dynamic Range, Back-Light Compensation
• No light - LWIR, MWIR, SWIR Imaging Technology
• Vibration effects – Electronic Image Stabilization, Gyro Stabilizers
• Atmosphere Fog/Haze/Dust/Smoke
As you can see, many challenges have been addressed and further improvements will be offered as video technology
evolves. Until recently, the ability of visible wavelength cameras to see through moderate to heavy
fog/haze/dust/smoke conditions has been either unavailable or far outside the price range of most customers.
That is, until now… CohuHD™ has once again risen to the occasion by leveraging increased computation power and
image processing algorithms to improve video performance. CohuHD has introduced within its Helios product family a
high definition 720p 30x optical zoom video camera that offers the first defog image processing feature available.
Defog Image Processing Benefits
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Extends visibility
Improves video quality (contrast, sharpness, color)
Effectively removes fog
Enhances real-time video
Provides better situational awareness in poor visibility, including incident detection
Applications
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Traffic monitoring
Video surveillance
Video security
Marine surveillance
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12367 Crosthwaite Circle | Poway, CA 92064
858.391.1800
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How CohuHD provides better video quality in bad weather and in the presence of atmospheric obscurants
How using CohuHD’s defog feature improves video image quality in poor visibility conditions, and helps to
increase awareness in critical situations such as car accidents, traffic monitoring and outdoor security
surveillance
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© 2013 CohuHD. All rights reserved.
Read this paper to discover:
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Defog Image Processing
Defog Video Enhancement for Better Video Quality
Video quality is a critical factor in video applications, especially in security surveillance and traffic monitoring. The
cameras must be able to see clearly and to produce clear video. Manufacturers have introduced megapixel and high
definition cameras with high quality lenses. However, image quality depends not only on the number of pixels on the
object, but also on color, contrast, gamma adjustment, etc.
Weather greatly affects video image quality captured by outdoor camera systems. Depending on weather conditions,
the color and contrast of video can be degraded dramatically. “Bad weather” factors such as rain, haze, vapor, dust, and
fog affect the quality of captured video. Traffic monitoring and border control must be done under all weather
conditions. It’s a major limitation to not be able to recognize if a moving object is a person or an animal, or to not be
able to see a license plate number. Outdoor camera systems, especially for surveillance, need to have functionality that
can remove unwanted bad weather effects - “fog” - from the video, to improve video quality.
CohuHD Video Defog Solution
CohuHD's Helios™ family of HD products is now available with the latest in HD (High Definition) 720p camera imaging
and optical technology, providing defog video enhancement processing capability. CohuHD’s real-time defogging
feature produces improved images in obscuring haze and foggy conditions commonly encountered during surveillance
and traffic monitoring.
HD
CohuHD 3960
Camera. Defog Function On
How does the defog function remove the obscuring effect (fog, mist, dust, smoke, etc.)? A contrast enhancement
algorithm is applied to the video signal before it leaves the camera. This is done in order to use all video data without
any loss during compression. The algorithm analyzes the density of obscurants, pixel by pixel, and applies contrast and
sharpness adjustments to the video using histogram analysis and other forms of image enhancement. Since the
algorithm executes within the camera, no additional latency occurs and the analysis is done in real-time. The amount of
image enhancement is dynamically modified based on fog density.
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The algorithm works in two steps: first, fog density of the scene in the frame is determined. Then, restoration of the
frame (signal correction) is done. The algorithm is fast enough to be applied in real-time on a frame-by-frame basis.
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12367 Crosthwaite Circle | Poway, CA 92064
858.391.1800
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Camera. Defog Function Off
© 2013 CohuHD. All rights reserved.
HD
CohuHD 3960
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Defog Image Processing
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858.391.1800
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Ensuring Security with CohuHD’s Defog Functionality
© 2013 CohuHD. All rights reserved.
Figure 1
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Defog Image Processing
Figure 2 demonstrates fog removal using the defog function. The picture on the left is taken on a foggy day with the
defog function off. The picture on the right is the same scene taken with the defog function on. Both pictures were
captured with a CohuHD 3960HD camera.
CohuHD 3960
HD
Camera. Defog Function Off
Figure 2
CohuHD 3960
HD
Camera. Defog Function On
For another example that demonstrates the effectiveness of the CohuHD defog function on a rainy, foggy day, please
click here to see it.
www.CohuHD.com
12367 Crosthwaite Circle | Poway, CA 92064
858.391.1800
CohuHD_HD_Defog_Image_Processing 082814
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Figure 3. Manual Defog Control
© 2013 CohuHD. All rights reserved.
The defog feature adjusts contrast, color, and sharpness. Figure 3 shows CohuHD’s current Defog Control, which
operates in manual mode. In this mode, the user selects one of three levels of enhancement, depending on fog
thickness – level 1 for light fog density, level 2 for medium, and level 3 for heavy. In the automatic mode, available soon,
the camera will automatically recognize the fog density and apply the necessary correction level. The Auto-Defog mode
will allow the defog function to be enabled full time. When no fog is detected there is no compensation. Still, the user
will be able to select to turn the Auto-Defog mode on or off.
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Defog Image Processing
Conclusion
CohuHD’s video enhancement functionality responds to the growing demand for outdoor camera systems that provide
increased visibility under bad weather and atmospheric conditions. CohuHD’s real-time defogging feature produces
enhanced video in haze and fog environments commonly encountered in surveillance and traffic monitoring. Many of
the factors that influence video quality can be controlled, but weather and atmospherics cannot. Using CohuHD’s latest
720p camera imaging technology - defog as discussed here, as well as electronic image stabilization, improvement of
low light sensitivity, and increased zoom magnification - ensures high quality video under varied and changeable
outdoor conditions.
About CohuHD
www.CohuHD.com
12367 Crosthwaite Circle | Poway, CA 92064
858.391.1800
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© 2013 CohuHD. All rights reserved.
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CohuHD is a leading manufacturer of high-definition video systems designed to satisfy the demanding performance
requirements for critical infrastructure applications. CohuHD solutions integrate the latest high-definition video imaging
and compression technologies into our ruggedized camera products. CohuHD is a high-value provider for monitoring in
critical, sensitive environments. For more than 50 years, we have been manufacturing the most reliable, rugged video
cameras available on the market. For more information on CohuHD’s products, please visit www.cohuHD.com. Follow us
on youtube.com/cohuhd, twitter.com/cohuhd, linkedin/company/cohuhd, and facebook.com/cohuhd.
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