Fourier transform webcam

by Dominic Ford

Normal view

Fourier transform view

Instructions

To use this page, you will need to have a webcam attached to your computer. You will probably receive a message from your web browser asking you to authorise this page to view images from your webcam, and you will need to click "OK".

The images above show a two-dimensional Fourier transform of the images seen by your webcam. Fourier transforms are important to many areas of physics – especially diffraction patterns in optics.

More information

A Fourier transform is a map of all of the frequency components that are present in a signal.

A two-dimensional Fourier transform, like the ones shown above, map out the spatial frequencies that are present in images seen by your webcam.

Bright spots represent length-scales where there is a lot of detail in the image, and dark areas show where there is little detail present. Long length-scales (low spatial frequencies) appear in the centre, while fine structure (high spatial frequencies) appear towards the edges.

Try holding up your five fingers to the camera, and rotate your hand and change the separation of your fingers. Also try pointing the webcam at stripy fabric, a check shirt, or a chess board.

The red, green and blue components of the image are Fourier transformed separately, so some colour information is preserved. Only the amplitude of the Fourier transform is shown; the phase is discarded.