Abstract
A new type phase-reading two-wavelength interferometer employing a single mode laser diode and a single detection modulated with a trapezoidal current waveform is demonstrated. This waveform consisted of two linear ramps and two flat levels. During the ramps, the laser frequency would be swept linearly and during the two flat portions of the waveform, the interference signals were separated using electronic circuits for pseudo-heterodyne detection. To solve the phase ambiguity problem in the interferometer after signal processing, trapezoidal modulation and pseudo-heterodyne techniques were applied.