Measurement of Two-Dimensional Small Angles Based on Interference Fringes

A novel two-dimensional small angles measurement is introduced, which is based on the relation between the interference fringes shape (direction and width) and the angle contained by two lights of Michelson interferometer, and utilizes quadrant Si-photoelectric detector (QPD) as detection device. The status of interference fringes changes from static to dynamic, with modulating the wavelength of the laser-diode (LD) by sawtooth modulation. To ensure that while LD is shining, the change of the wavelength of the LD is linear, this paper adopted sawtooth modulation signal (500 Hz) with a DC offset. Using High Speed A/D Convert Card (250 K) and software to collect analogue signal, and data processing technique to got the swing angle. The test precision is 0.05"calculated by experiment data.