Shearing interferometers are very popular and have a growing range of
applications, especially in the field of optical testing. We describe
a new kind of a lateral shearing interferometer. The lateral shear is
produced by two Ronchi phase gratings in series. The phase can be shif
ted by a lateral movement of one grating relative to the other, and th
e amount of shear can easily be adjusted by variation of the distance
of the gratings. The simplicity of the device is an important advantag
e, especially in the near IR. (C) 1997 Optical Society of America.