Lastek: Photonics Technology Solutions

BOS imaging of a thermal flow

Background Oriented Schlieren: BOS Imaging

For the visualization of gas motion based on local refractive index variations LaVision's Background Oriented Schlieren (BOS, also known as Synthetic Schlieren) is a simple and cost-effective alternative to laser imaging methods, because it doesn’t need any complex illumination device like a laser needed for laser imaging, and it works without seeding the flow.

BOS is a line-of-sight imaging technique and measures locally the density gradient as an integrated value over the line-of-sight. In practice, only a random dot pattern in the background of the flow is imaged with a high resolution camera before and during the test. By comparing the two pictures (or more precisely correlating the two patterns similar to the image correlation in PIV) the local displacement of the background pattern can be used to provide lateral information on path-integrated refractive index variations.

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3D temperature field over a cup of coffee

LaVision’sTomo-BOS imaging systems measure quantitatively density or temperature fields in 3D using multiple camera BOS projections. This 3D imaging technique requires an accurate geometrical calibration of the multi-camera system and an iterative tomographic reconstruction algorithm.

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The modular concept of LaVision’sFlowMaster Underwater PIV systems allows a large variety of PIV imaging configurations for uncompromised performance. 2D-, Stereo- and Tomo-PIV measurements are realized using torpedo designs or compact vertical borescope setups. The submarine housings consist of high quality stainless steel tube components containing the remotely controlled PIV camera(s) and sheet optics. Hydrofoils cover the stiff vertical support tubes for minimum drag and wake. The laser and electronic components are accommodated in watertight housings mounted on the carriage above water level. The whole construction is CFD optimized and carefully tested up to a maximum towing speed of 7 m/s at a water depth of 1.5 m.

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LaVision’s new DaVis 10 defines a new landmark of cutting-edge innovations in Intelligent Laser Imaging software. Combining high-performance cameras with outstanding image processing algorithms opens new dimensions for your imaging applications. DaVis 10 has been redesigned from the ground-up to deliver a software for modern demands for usability, data handling and visualization.

LaVision's DaVis 10 defines a new landmark of cutting-edge innovations in Intelligent Laser Imaging software. Combining high-performance cameras with outstanding image processing algorithms opens new dimensions for your imaging applications. DaVis 10 has been redesigned from the ground-up to deliver a software for modern demands for usability, data handling and visualization.

Leading-edge 4D imaging

DaVis 10 includes LaVision’s most innovative algorithms for 4D measurements of flow fields, sprays, mixing and combustion processes and 3D surfaces. Latest innovations like the robot-assisted MiniShaker for high-density particle tracking with Shake-the-Box, Pressure from PIV and Tomographic LIF provide a comprehensive platform for Intelligent Imaging.

Scalar Imaging in Mixing Fluids and Thermal Flows

LaVision’s FluidMaster laser imaging systems measure scalar flow properties such as concentration, mixture fraction, fluid composition and temperature in various fluid dynamical applications. For scalar laser imaging in fluids Laser Induced Fluorescence (LIF) is the most versatile and practical measurement technique featuring high signal levels and spectral selectivity.

Beside accurate signal calibration the LIF software package in DaVis supports preprocessing routines accounting for background offset, nonuniform laser sheet profile, laser pulse-to-pulse fluctuations, image vignetting and distortion.

For LIF imaging accurate flow seeding with LIF-active molecular flow tracers is required and essential for successful measurements. LaVision has strong expertise in flow seeding including the appropriate use of each flow marker and in providing the necessary seeding device.

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Advanced Flow Field Imaging in Fluid Mechanics

Particle Image Velocimetry (PIV) as well as Particle Tracking Velocimetry (PTV) are recognized as the most powerful and practical diagnostic tools for flow field analysis in fluid dynamics applications. Instantaneous 2D and 3D flow images are measured with high spatial and temporal resolution. LaVision’s FlowMaster PIVsystems have been generating valuable insights into flow phenomena in scientific, engineering, biological and medical applications for many years. Constant technological advances in hardware and implementation of the latest research of algorithms assure the maximum in performance, accuracy and system operability.

Our FlowMaster models are application oriented, meeting a wide range of measurement requirements due to their modular and flexible system design.

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