Interferometer apparatus for microtopography
Ring resonator gyro
Synthetic heterodyne demodulator circuit
Interferometric, self-homodyne optical receiver and method and optical transmission system incorporating same Patent #: 5319438
ApplicationNo. 189931 filed on 02/01/1994
US Classes:356/482, For distance or displacement measurement356/498Displacement or distance
ExaminersPrimary: Turner, Samuel A.
Assistant: Eisenberg, Jason D.
Attorney, Agent or Firm
International ClassG01B 009/02
Foreign Application Priority Data1993-02-23 DE
AbstractA phase-modulated interferometer has improved control and signal processing. Superimposition signals capable of evaluation in a phase-modulated interferometer without a complicated sawtooth control of the phase modulator are attained, in that two sinusoidal control signals which have modulation frequencies (ω1, ω2) and are rigidly coupled with respect to phase and frequency are applied to the known phase modulator and a cosine signal which is used in a conventional manner for evaluating the phase displacement is filtered of the superimposition signal generated in the interferometer by an electronic bandpass filter. At the filter frequency (ωF) of the bandpass filter, an odd-number harmonic and an even-number harmonic of the two modulation frequencies (ω1, ω2) have the same frequency, when the amplitudes ($c;1, $c;2) of the control signals satisfy the condition for the suitable operating point of the phase modulator. The improvement has application to phase-modulated interferometers, in particular, for precision distance measuring devices, preferably by the heterodyne evaluating method.