The The Imaging Source cameras are provided with a 5mm distance ring from factory. This ring is needed, if a C-mount lens is in use. If a CS-mount lens is used, then this 5mm distance ring has to be removed. If this is done wrongly, then only unsharp, blurry image are provided and it is impossible to focus.
It can happen that the ring is removed together with the protection cap from the camera:
The "Ring together with protection cap" shows, how it looks like if the 5mm Distance ring was unscrewed with the protection cap from the camera. The both parts in the middle and right side show, how the cap and the 5mm ring are separated.