Vexcel Imaging Unveils A New Software-Based Solution For The Correction Of Motion Blur
An essential quality feature of good imagery is how well detail and thus, ultimately, information can be recognized from them. If significant detail can be distinguished, an image has a…
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An essential quality feature of good imagery is how well detail and thus, ultimately, information can be recognized from them. If significant detail can be distinguished, an image has a high level of sharpness. Achieving this goal is not always easy, as so-called motion blur is a well-known problem in photography, especially when taking high-quality photos of moving objects or capturing when the camera position is not entirely stable. What can be achieved in everyday photography from short shutter speeds, or the use of a tripod with quite simple means, turns out to be much more complex in aerial photography. Due to the forward movement of the aircraft, the platform is necessarily always in motion which is why a blurring of the image content must be expected in any situation. Since high-quality image data is the basic requirement for photogrammetric applications, this motion blur must be corrected.
In the past, there have been different approaches to correct motion blur. The solutions ranged from moving film in analog cameras, time-delayed integration (TDI) on CCD sensors, mechanically moving CMOS sensors, to the simple use of fast shutter speeds. What all these approaches have in common: they compensate for image blur only in the direction of flight–so they are all Forward Motion Compensation (FMC). However, since an aircraft can also move in other directions due to external circumstances such as changes in the air, these approaches fall short.
Vexcel Imaging, a provider of large-format aerial cameras, now has a new innovative approach to motion compensation. With their Adaptive Motion Compensation (AMC), all camera motion can now be corrected during flight, regardless of direction. This new multi-directional compensation is software-based, eliminating mechanical parts that can wear out or malfunction.
Image motion using known orientation data
The so-called image motion, the influence of the aircraft’s motion on the image, is calculated within AMC using three factors. First, known orientation data from the navigation unit with GNSS and IMU are used. Second, the approximately known object geometry, i.e., the motion of the camera relative to imaged object, is used. And third, very precise parameters of the camera describing the imaging process and known from the camera calibration serve as a valuable source of information. The underlying idea is that the blurred image and the sharp image hidden within are connected via a so-called “blur kernel”. If this blur kernel is known, a mathematical deconvolution operation (inverse operation for convolution) can be used to calculate the sharp image from the blurred one.
See The Scientific Paper For More Details
Adaptive Motion Compensation was developed specifically for 4th generation UltraCam sensors. It is available via UltraMap processing software from Vexcel Imaging. “The use of AMC to successfully compensate for multidirectional motion represents a turning point for the industry,” Alexander Wiechert, CEO of Vexcel Imaging, is certain. “The main advantage is the software-based solution. The second important advantage is the concept’s ability to handle any kind of motion blur, be it forward motion along the trajectory or angular motion of the camera.” Wiechert additionally noted that another advantage of the solution is its ability to adapt to varying degrees of blur in the image, depending on the object scale or image position, concluding that “AMC makes our 4th generation UltraCam sensors even more powerful.”
Proven and reliable solution
The first fourth-generation aerial camera to apply AMC to correct image blur is the UltraCam Osprey 4.1. As aversatile system, it simultaneously captures nadir images in photogrammetric quality (PAN, RGB and NIR) and oblique images (RGB) in four directions.
The UltraCam Osprey 4.1 meets diverse application needs ranging from 3D mapping to traditional mapping applications from the same flight mission.
Learn More About UltraCam Osprey 4.1
UltraCam Osprey 4.1 • Aerial camera for nadir & oblique image capture (vexcel-imaging.com)
In a project in London, Vexcel Imaging demonstrated how powerful the 4th generation systems are, especially in practical use. An urban area was flown with 3.5 centimeters ground sample distance with an UltraCam Osprey 4.1 at an altitude of 750 meters. The airspeed was 126 knots and the exposure time was 1 millisecond. Due to strong turbulences during the flight, the captured images were initially blurred and of insufficient quality. Only by using AMC could aerial images finally be produced in which building facades, as well as fine structures, were clearly recognizable.
