Shearing interferometer
（重定向自Shear plate）
![Principle of the shearing interferometer.](/Images/godic/202502/10/Shearing-interferometer4009.png")
![](/Images/godic/202502/10/Shear-plate4009.png")
The shearing interferometer is an extremely simple means to observe interference and to use this phenomenon to test the collimation of light beams, especially from laser sources which have a coherence length which is usually a lot longer than the thickness of the shear plate (see graphics) so that the basic condition for interference is fulfilled.