How to remove Schlieren from an image?

[Jörn]

Dear all!

I have got an image from a slowly changing illumination distribution. But there are schlieren, i. e. loopy stripes appearing brighter than the surrounding area. The schieren are due to imperfection of the material which is imaged. Please find attached a typical image.

How can I remove these patterns from the image? Simply smoothing the image does not remove the pattern.

Does someone has experience using Fourier transformation or using wavelets to remove such patterns and could give me some hints? 

Best regards

Jörn

[CarstenS]

Hi Jörn,

maybe it would be a good idea to use diffuse light, e.g. domelight as removing those Schlieren could be hard as they change on every image

Kind regards

Carsten

[1100fps]

If this is a fixed pattern, or does it change?  Is there useful informaion in the picture (that was posted) you want to keep?  If the image you showed is of what should be a null filed, you may very well use image subtraction to subtract out the variaion on all subsiquent frames.

The penalty is loss of bit depth on the final image, however, the image you show will not cause a huge bit depth loss.

Rob