Abstract
We introduce a holographic wide angle system that combines the accuracy of a long focal length with the extended field of view of a wide angle lens. To accomplish this, we use a computer-generated hologram (CGH) in front of the lens to diffract light from (a discrete number of) specific angular locations. This method is tested in laboratory conditions, as well as under real-world conditions. This measurement system was developed as a possible tool for real-time movement tracking and control of extended dynamic structures, such as bridges and high-rise buildings. Within that application, the obtained measurement uncertainty is 10 μm in object space at 10 m distance spanning 10 m width.
Highlights
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Even extremely slight angular changes lead to large measurement errors for deformation measurements. Another approach is to avoid this problem by using a short focal length in combination with extremely accurate image processing. We have shown such an approach in previous publications [11–14] where we employed computer-generated holograms (CGH) in order to achieve accuracies in the range of hundreds to thousands of a pixel
The incident peripheral beams are diffracted at the CGH to become approximately on-axis beams
Summary
There could be a large number of structures which could benefit from an installation of deformation sensors, even though they are not adaptive and were not meant to be equipped with them. For adaptive systems, which are feedback controlled, it is imperative to achieve high spatial accuracy (sub-mm), high temporal accuracy (100 Hz) as well as low latency (few ms) for multi-modal oscillation detection/measurement. Total stations and terrestrial laser scanners are far more common, especially when used in the construction of buildings and bridges Nowadays, they come with absolute distance meters, which offer sub-mm longitudinal and a few mm lateral accuracy over a 100 m distance [6]. They come with absolute distance meters, which offer sub-mm longitudinal and a few mm lateral accuracy over a 100 m distance [6] They lack high refresh rates for large. The following sections are focused on eliminating this shortcoming for a discrete number of measurement points
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