According to some embodiments, housing for OCT is, (a) less than 5mm internal diameter (e.g. less than 2 mm, 1.5 mm or less in some embodiments), a first end, a second end a tubular body having, (b) first from the end formed on the tubular body at a position shifted from the second end to a position close to the second end window, the tubular body surrounded by a portion of, and a window having a width w. According to some embodiments, a 0.05mm
