Image stabilization
From Wikipedia, the free encyclopedia
Image stabilization is a family of techniques to increase the stability of an image. It is used in image-stabilized binoculars, photography, videography, and astronomical telescopes. With still cameras, camera shake is particularly problematic at slow shutter speeds or with long focal length (telephoto) lenses. With video cameras, camera shake causes visible frame-to-frame jittering in the video recorded. With astronomy, these problems are compounded by variations in the atmosphere over time, which causes the apparent position of objects to move.
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[edit] Techniques of image stabilization
[edit] Optical Image Stabilization
An Optical Image Stabilizer, often abbreviated as OIS, is a mechanism used in a digital still camera or video camera that stabilizes the recorded image by varying the optical path to the sensor.[1] In Canon's implementation, it works by using a floating lens element that is moved orthogonally to the optical axis of the lens, using electromagnets. The vibration signal which is compensated for by the stabilizing lens element is typically aquired using two piezoelectric angular velocity sensors (often also called gyroscopic sensors).[2]
[edit] Moving the image sensor
The sensor capturing the image may be moved in such a way as to counteract the motion of the camera. Konica Minolta used a technique called "anti-shake" now marketed as SteadyShot in the Sony α line, which relies on a very precise angle speed sensor to detect camera motion.[3] Other manufacturers use DSPs to analyze the image on the fly and then move the sensor appropriately.
[edit] Digital image stabilization
Digital image stabilization is used in some video cameras. This technique shifts the electronic image from frame to frame of video, enough to counteract the motion. It uses pixels outside the border of the visible frame to provide a buffer for the motion.
[edit] Stabilization filters
Many Non-linear editing systems use stabilization filters that can correct a non-stabilized image by tracking the movement of pixels in the image and correcting the image by moving the frame. The process is similar to Digital image stabilization but since there is no "larger" image to work with the filter ether crops the image down to hide the motion of the frame or attempts to recreate the lost image at the edge through extrapolation.
[edit] Orthogonal Transfer CCD
Used in astronomy, an orthogonal transfer CCD (OTCCD) actually shifts the image within the CCD itself while the image is being captured, based on analysis of the apparent motion of bright stars. This is a rare example of digital stabilization for still pictures. An example of this is in the upcoming gigapixel telescope Pan-STARRS being constructed in Hawaii.[4]
[edit] References
- ^ What is Optical Image Stabilizer?, Technology FAQ, Canon Broadcast Equipment
- ^ Glossary : Optical : Image Stabilization, Vincent Bockaert, Digital Photography Review
- ^ Dynax 7D Anti-Shake Technology, Konica Minolta
- ^ Pan-STARRS Orthogonal Transfer CCD Camera Design, Gareth Wynn-Williams, Institute for Astronomy
- gyroscopic stabilization in aerial photography, Multimedia: Use Image Stabilization, Andy King, Web Site Optimization, 2004
