Abstract
Lytro cameras are equipped to capture 3D information in one exposure without the need for structured illumination, allowing greyscale depth maps of the captured image to be created using the Lytro desktop software. These consumer-grade light-field cameras (Lytro) provide a cost-effective method of measuring the depth of multiple objects which is suitable for many applications. But, the greyscale depth maps generated using the Lytro cameras are in relative depth scale and hence not suitable for engineering applications where absolute depth is essential. In this research, camera control variables, environmental sensitivity, depth distortion characteristics, and the effective working range of first- and second-generation Lytro cameras were evaluated. In addition, a depth measuring technique to deliver 3D output depth maps represented in SI units (metres) is discussed in detail exhibiting the suitability of consumer-grade Lytro cameras suitability in metrological applications without significant modifications.
Highlights
Measuring the depth of a scene using digital cameras is becoming a common technique used in many engineering fields
The sensitivity curve is a method of expressing the relationship of how depth values measured using a Lytro light-field camera can be expressed in SI units
Consumer-grade light-field cameras have become reality in recent years and potentially present a single camera, single position solution to 3D imaging, reducing the complexity of measurement alignment and transducer numbers, which is of very significant interest to the machine vision community
Summary
Measuring the depth of a scene using digital cameras is becoming a common technique used in many engineering fields. Techniques to generate scene depth data using 2D cameras involved capturing multiple images of the same scene by changing the camera position (z axis) [1, 2], aperture diameter, and focal length [3,4,5] These methods may be suitable for some applications that require only nonparameterised depth data, i.e. different depths represented by varying relative greyscale values. The purpose of the research presented here is to define the potential for commercial consumer-grade light-field cameras (in this case Lytro cameras) for measuring scene depth in absolute (in this case SI units) with the potential for engineering metrology applications. This work extends previous definitions of the accuracy and the repeatability capability of such cameras [15], defines possible environmental conditions when these values may be achieved, and provides performance benchmarks with this lower end yet cost-effective technology to allow exploration as a potential 3D coordinate metrology solution, in preference to other multi-camera or multi-view solutions
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