everyday life - Explaining the diffraction pattern of a lightbulb filament

This really nice video from the Royal Institution channel on YouTube has a gorgeous shot of the diffraction pattern caused in laser-pointer light by the helically-coiled filament of a light bulb:

There's multiple interesting features going on here and I would be interested in a more in-depth explanation of what causes them, that goes beyond the simple "because diffraction". As explained in the video, a helical coil can be seen roughly as two collections of line segments, which explains the cross-like structure, but there is also

• light on the outside of the cross but not inside the narrower angle,


• a definite double-period structure on the lower-left arm of the cross,


• a bi-periodic structure in the light on the obtuse angle of the cross,


• an offset between the cross arms at the vertex, I should think, and


• a global ring structure superposed on everything,

and that's just from a first glance. What causes these features, and what can they say about the structure of the filament?

(If that's too complicated, I would be happy with a good reference to a readable introduction to the diffraction patterns caused by helical structures.)