The outer ring has lenses to focus IR light, and a hole for the camera lens.

The six infrared LEDs are on a thick board, with an aluminum heat spreader, and a connection to two solid metal blocks attached to the sensor board.

The lens is manually focused and secured with what looks like hot melt glue (this may cause focus issues over time).

There is just one piece of filter glass, flipped in place for day mode (higher end cameras use separate glass for day and night mode).

The optical sensor is at the bottom of the stack. It's surrounded by a clear plastic sticker (if you know why, post in the comments!).