Two-dimensional focusing laser differential interferometer and flat plate boundary layer density pulsation measurement method

The invention discloses a two-dimensional focusing laser differential interferometer and a flat plate boundary layer density pulsation measurement method, which belong to the field of flow field measurement. The two-dimensional focusing laser differential interferometer comprises a laser differential interferometer which consists of an optical signal transmitting unit, a first cylindrical lens, asecond cylindrical lens, a third cylindrical lens, a first prism, a second prism, a first polarizing film, a second polarizing film and a photoelectric conversion unit, wherein an optical signal of the optical signal transmitting unit sequentially passes through the first cylindrical lens, the first polarizing film, the first prism, the second cylindrical convex lens, the third cylindrical convexlens, the second prism and the second polarizing film and then reaches the photoelectric conversion unit. When a boundary layer of a flat plate is being measured, an optical path focus point is placedin the boundary layer of t