We present a new methodology for ray-tracing analysis of volume holographic imaging (VHI) systems. Using the k-sphere formulation, we apply geometrical relationships to describe the volumetric diffraction effects imposed on rays passing through a volume hologram. We explain the k-sphere formulation in conjunction with ray tracing process and describe its implementation in a Zemax UDS (User Defined Surface). We conclude with examples of simulation and optimization results and show proof of consistency and usefulness of the proposed model.
We present a high-speed and low-cost approach for structured light pattern sequence projection. Using a fast rotating binary spatial light modulator, our method is potentially capable of projection frequencies in the kHz domain, while enabling pattern rasterization as low as 2 μm pixel size and inherently linear grayscale reproduction quantized at 12 bits/pixel or better. Due to the circular arrangement of the projected fringe patterns, we extend the widely used ray-plane triangulation method to ray-cone triangulation and provide a detailed description of the optical calibration procedure. Using the proposed projection concept in conjunction with the recently published coded phase shift (CPS) pattern sequence, we demonstrate high accuracy 3-D measurement at 200 Hz projection frequency and 20 Hz 3-D reconstruction rate.
Many of the large components of modern gas turbines are cast, resulting in rough surface profiles, which have to be machined to achieve the component’s final state. As there are high deviations in casting components, the real geometry does not meet the ideal model dimensions and is known neither to the supplier nor to the customer. While manual 3D-scanning processes, heavily depending on the operator’s qualification, get more attention, conventional means are still the basis for quality assurance of such parts.
Although significant time reduction can be reached by automated scanning, there is still a low variety of corresponding applications for large components on the market. Flexible systems are an approach for further development as most of the manufacturers handling large components already have and use machine tools for the processing of their components.
The designed and implemented prototypical system allows the acquisition of a large component’s surface with only a few manual inputs prior to the actual scanning procedure. It can be used with existing machining tools, allowing an easy implementation for different use cases of a pre-manufacturing scan, e.g. for CAM planning. The application is implemented in a small software tool that can be adapted to other machines with low effort. The implementation has been demonstrated in a real manufacturing environment with typical environmental conditions in the shop floor. The prototypical application has been built mainly with existing components.
Following the V-Model, each domain has been investigated individually followed by a complete system investigation. With a system price below 100.000€ the price is below 10% of most automated systems on the market. The presented cost efficient, low complexity prototypical system can provide early information about the product for a digital process chain in industry 4.0, enabling flexible, intuitive and easy integration.
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