Looks perfectly fine, though it is very odd for it to look like that after 3 weeks. I don't think it's an infection, just an odd fermentation.
Do you have any idea how much yeast you pitched? How long of a lag time did you have before you started seeing activity?
My guess is you pitched a suboptimal yeast count. Did you make a starter? You need about 0.75 million cells per ml wort per degree plato. For an OG of 1.050, that's about 175 billion cells. A smack pack or a white labs tube will give you at most 100 billion, though the viability could be significantly less depending on how it has been handled.
You should end up with good beer regardless, it's just that the fermentation will go slowly and it could possibly end up underattenuated. Also, when the yeast have to spend an unusual amount of time propagating rather than getting it out of the way and proceeding with fermentation, you could end up with high levels of esters, fusel alcohols, aldehydes, and/or diacetyl depending on the strain.