How to use computational imaging to reveal hidden details

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In computational imaging a number of images of the same field of view are acquired under different lighting or optical conditions. Data is then extracted from these to create a new image containing information that cannot be obtained from a single-shot image. Stemmer Imaging offers a choice of powerful computational imaging solutions so is well placed to explain the technology.

The computational imaging process might involve changing the intensity, angle or wavelength of illumination for each image. By choosing from multi-segment, multi-spectral or multiple independent lights, a number of different imaging enhancements can be obtained. These range from creating higher contrast ratios (high dynamic range) to revealing previously invisible surface defects.

Stemmer Imaging can provide general-purpose computational imaging systems such as the computational imaging kit from CCS as well as its own trevista surface inspection systems.

Computational imaging applications

The CCS computational illumination kit can be used with any machine vision camera and most smart cameras. It includes an extensive choice of four-quadrant ring or bar lights, full-colour, multi-spectral or segmented full-colour lights, as well as a four-channel light sequencing switch, software and cables. A lighting sequence can be programmed on the four channels to trigger the external camera exposure automatically. The system is fully compatible with Sherlock machine vision software from Teledyne DALSA, which carries out the computational imaging processing on the acquired images.

Typical computational imaging techniques include:

  • High Dynamic Range imaging (HDR) - creating images with higher contrast ratios
  • Ultra-Resolution Colour (URC) - creating higher-resolution colour images with no interpolation artifacts
  • Extended Depth of Field (EDOF) - improving measurements without losing light or reducing magnification
  • Bright Field/Dark Field - combining the advantages of two well-known lighting techniques
  • Multi-spectral Imaging - enhancing images with maximum contrast from multiple spectral bands
  • 360-degree object capture - panoramic imaging with singly triggered, multiple scene acquisition

Stemmer Imaging trevista surface inspection systems

A special application of computational imaging is 'shape from shading'. Stemmer Imaging's patented trevista shape from shading approach reliably detects very small defects on shiny and curved surfaces or materials with variable brightness that are normally very challenging. The trevista technology provides fully automated, process-safe, 100 per cent inspection of the texture and the topography of the surface. The object is illuminated from four different directions using domed diffuse structured light to reduce interference from ambient light. Defects down to a few microns can be detected and the separate inspection of texture and topography enables real defects such as scratches to be easily distinguished from supposed defects such as dirt on surfaces.

Stemmer Imaging offers a choice of dedicated trevista systems. The trevistaCAM is completely self-contained, featuring a 4 megapixel industrial smart camera, complete with measurement software, integrated into a domed diffuse structured lighting system. Three modular CVS trevista systems are also available with a choice of cameras. The 'Surface' system is designed for the inspection of static parts with cycle times up to 200 parts per minute. The 'Cylinder' system uses a line scan camera for the inspection of cylindrical components, while the 'Multiline' system is designed for the inspection of moving or rotating components.

For more information about Stemmer Imaging and computational imaging systems, go to

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