Investigation of characteristic for the combination of MEMS mirror and F-theta lens applied in all fiber coupled infrared heterodyne interferometry

Heterodyne interferometer is a well-know optical device widely used in a variety of applications, including mapping the surface of glass, measuring the thickness of the film, and obtaining the stress distribution of the sample. This technique offers advantages of non-contact, higher lateral and vertical resolution. In recent years, the fiber-coupled infrared heterodyne interferometer has been extensively developed because of the eye-safe wavelength. However, the sample is scanned by the motor in the conventional heterodyne interferometer, which may limit the lateral accuracy of the heterodyne interferometer system. In other papers, some optical components are moved by the motor in some interferometers, which may enhance the lateral accuracy, but the sample can not be scanned with the constant velocity. In this paper, an all fiber coupled infrared heterodyne interferometer based on the combination of the microelectromechanical systems (MEMS) mirror and F-theta lens set is developed. The effective reflective mirror covers an area of 1mm², and diameter of the output beam from the F-theta lens equals to 100mm.