Unsharp photos at high velocity

Applies to

Sensoft Vision

Issue

At high filament velocity (e.g. over 1200 m/min) the photos of the defects are not sharp.

Solution

We have to decrease the illumination time of the photo, i.e the value of the field Flash duration [µs] on the Main page. This because the blurring is equal to the distance the filament runs during the illumination time, e.g. for illumination time 1 µs and velocity 1200 m/min = 20 m/s = 20 µm/µs we get a blurred distance = illumination time × velocity = 20 µm.

You can decrease the illumination time without getting darker photos by increasing the field Gain [dB] in the Advanced settings on page Settings. You can increase the gain to 35 dB without more noise on the picture and to 40 dB with little more.

Typically this will allow to lower the illumination time to below 0.2 µs. It is also advised not to go below 0.1 µs, because the efficiency of the illumination (i.e. the image brightness divided by Flash duration) starts to decrease.

If you still need to decrease the illumination time, you can enlarge the iris of the camera optics to keep the brightness of the images. This is not a software setting, but must be done at camera optics itself. It should be used only as last resort, because it reduces the depth of field, i.e. the distance between the nearest and the farthest objects that are in acceptably sharp focus. Our introductory video explains how to change the iris. if the cover lid is on, it has to be taken off.