Abstract
We describe an improved design of fiber-optic interferometer intended to measure surface profiles with enhanced capability of vibration suppression. The reference wavefront is generated directly from the measurement wave using a multi-mode fiber that eliminates only the spatial wavefront distortion by means of bend loss. The temporal fluctuation caused by vibration is consequently cancelled out in the process of interference since it becomes to exist in both the measurement and reference waves. Further, an injection locking technique is incorporated to stabilize the reference wave intensity and hence make stable the interferometric fringe intensity. Experimental result proves that the proposed fiber-optic interferometer is capable of producing sub-wavelength measurement precision even in the presence of severe vibration with 100-μm amplitude.
Highlights
Optical interferometers are widely being used with various system configurations for testing optics such as lenses and mirrors
An example is the approach of single-shot fringe measurement, which was successfully demonstrated by means of Fourier-transform analysis [1], spatial phase shifter [2], diffractive optics [3] and pixilated phase mask [4]
Our design of fiber-optic interferometer offers a significant improvement in vibration desensitization capability by generating the reference wavefront directly from the measurement wave using a multi-mode fiber together with an injection locking scheme
Summary
Optical interferometers are widely being used with various system configurations for testing optics such as lenses and mirrors. An example is the approach of single-shot fringe measurement, which was successfully demonstrated by means of Fourier-transform analysis [1], spatial phase shifter [2], diffractive optics [3] and pixilated phase mask [4]. Another approach was direct suppression of vibration by implementing closed loop control in real time [5]. An injection locking scheme is incorporated to stabilize the reference wave intensity and sub-wavelength measurement precision can be achieved even in the presence of severe vibration with 100-μm amplitude
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