Image Processing Reference
In-Depth Information
Chapter 5
Image-Stabilization Systems
Simplified
5.1 Introduction
Image-stabilization systems can take on a wide range of designs ranging from very
simple to extremely complex in order to accommodate the needs of a specific appli-
cation. While these systems can be very diverse, all of them have a great deal in
common. Image-stabilization systems are built around a sensor, a wavefront com-
pensator, and a control system that connects these two components. The major dif-
ferences between systems are often limited to the components selected and the so-
phistication of the controller.
In the previous chapters, the sensor and compensator components were intro-
duced. This chapter explores the integration of these components and introduces a
simple image-stabilization system. This model system can be constructed in almost
any laboratory and provides a simplified example of a working tip-tilt system.
5.2 Integrating Sensor and Compensator
Image-stabilization systems are comprised of three main components: the wave-
front sensor, the compensation device, and a control computer, which includes the
electrical interfaces to read the sensor and control the compensator. Many different
sensors as well as compensators are available in the commercial market so many
unique image-stabilization systems can be constructed. The choice of components
for a specific system is based on the intended application and its specific properties.
For the most part, this is based on the operating bandwidth required to stabilize the
image to the desired level.
An image-stabilization system for an astronomical telescope is a good example
system to explore, as the optical system of a telescope is well defined. The basic
problem of image stabilization on optical telescopes is to keep the image of the as-
tronomical object on a fixed location in the focal plane. In the case of the image of a
star, this means keeping the centroid of the focused spot at a fixed location in the fo-
cal plane. The bandwidth required to keep the centroid of the star fixed depends on
what disturbances the system is designed to compensate. Correcting for the fast
motion of the atmosphere requires considerably higher bandwidth than the slower
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