Extended Depth of Field (EDOF)

Improve measurements without losing light or reducing magnification

Computational Imaging
Extended Depth of Field (EDOF)

Extended Depth of Field (EDOF)

Improve measurements without losing light or reducing magnification

All images have a depth of field (DOF), a distance over which objects appear in sharp focus. In any single image, DOF is limited by the magnification and aperture size used. In some machine vision applications, the DOF may not be great enough to focus sharply on all the objects in a scene. Conventional solutions for increasing DOF such as closing the aperture (higher f/#) come with substantial tradeoffs such as decreased light and less resolution.

The EDOF computational imaging technique allows an image to be created with a DOF greater than any of the single images. Using EDOF image processing software and the CCS computational illumination kit, multiple images with various depths of field can be merged to return a clear, sharp result - without loss of light or resolution.

How to get a lot more depth of field

To extend DOF, several input images captured at different focal planes are necessary. While there are a number of methods for EDOF imaging, two common ones are:

  • Using motorized or liquid lenses with white or monochromatic light to vary the focal point
  • Using a chromatically uncorrected lens along with multiple wavelengths of light to induce focal plane shifts
Three separately focused images producing a single EDOF image within an extended depth of field CCS computational imaging application
Inspection of fasteners
Inspection of fasteners
Inspection of fasteners

The example to the left merged three separately focused images to produce an EDOF image with all three fasteners in sharp focus.