Interference fringe detection system for distance measuring interferometer (original) (raw)
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Precise interferometric length measurement using real-time fringe fitting
Optik, 2011
We created a simple device for the measurement of nanoscale displacements consisting in a Twyman-Green interferometer with one mirror having a slight offset in the horizontal plane with respect to the direction perpendicular to the incoming beam and one mobile mirror, a CCD array camera that captures frames of fringes (interferograms) generated by the interferometer and a software that acquires the interferograms captured by the camera and fits the fringes in order to determine the initial spatial phase of the series of fringes and, consequently, to monitor the movement of the mobile arm of the interferometer. Because the interferograms were acquired and analyzed sequentially, the algorithm could be parallelized easily on a multiprocessor/multicore platform. The device can work in real-time in which case the maximum speed of the mobile arm of the interferometer for which we can obtain unambiguous results is 30 /8/s, which is, assuming a He-Ne laser as the light source, almost 2.5 m/s. In real-time conditions, the precision and accuracy of the measurement are low. In stationary conditions, however, the precision was determined to be below 1 nm.
Fringe-counting technique used to lock a suspended interferometer
Applied Optics, 1994
We implement a digital fringe-counting technique to measure in real time the relative mirror displacement of a suspended Michelson interferometer with modulated optical path length for oscillations much larger than the laser wavelength (). This provides the proper error signal for a servo mechanism that reduces the relative displacement within X/2. The implemented technique does not require extra optics or polarizers and thus can be used for interferometric gravitational wave detectors as a starting procedure to get the system locked.
Fringe analysis in scanning frequency interferometry for absolute distance measurement
Fringe 2005
A novel technique to measure absolute distances is presented. It is based on a Michelson interferometer where two tuneable lasers are superposed to create a synthetic wavelength. Relative and absolute interferometry theories are merged together. Its experimental realization allows absolute distance measurements with subfringe resolution. Preliminary results are presented in this work.
Novel micro interferometer for length measurements
Journal of Non-Crystalline Solids, 2004
A novel micro interferometer for length and displacement measurements based on sampling an optical standing wave was developed. The interference of two laser beams propagating in opposite direction results in a sinusoidal light intensity profile, which can be detected by thin transparent photodiodes. Two detectors positioned on the optical axis of a standing wave allow bi-directional fringe counting. The operation principle of a setup consisting of a phase sensitive transparent detector based on two integrated nip-diodes of amorphous silicon and its alloys will be discussed. Lissajous figures close to a perfect circle are recorded to demonstrate the operation principle of the new device.
A robust sinusoidal signal processing method for interferometers
Sixth International Symposium on Precision Mechanical Measurements, 2013
Laser interferometers are widely used as a reference for length measurement. Reliable bidirectional optical fringe counting is normally obtained by using two orthogonally sinusoidal signals derived from the two outputs of an interferometer with path difference. These signals are subject to be disturbed by the geometrical errors of the moving target that causes the separation and shift of two interfering light spots on the detector. It results in typical Heydemann errors, including DC drift, amplitude variation and out-of-orthogonality of two sinusoidal signals that will seriously reduce the accuracy of fringe counting. This paper presents a robust sinusoidal signal processing method to correct the distorted waveforms by hardware. A corresponding circuit board has been designed. A linear stage equipped with a laser displacement interferometer and a height gauge equipped with a linear grating interferometer are used as the test beds. Experimental results show that, even with a seriously disturbed input waveform, the output Lissajous circle can always be stabilized after signal correction. This robust method increases the stability and reliability of the sinusoidal signals for data acquisition device to deal with pulse count and phase subdivision.
Development of a fringe sensor based on 3x3 fiber optic coupler for space interferometry
SPIE Proceedings, 2005
Large stellar telescope is indispensable for astronomy. Aperture synthesis is a well-known technique to simulate a large space telescope by an array of small telescopes. Condition for aperture synthesis is that the light of the telescopes have to be combined coherently. Therefore, an interferometric Fringe Sensor (FS) to detect and stabilize the Optical Path Difference (OPD) between light from the different telescopes is required. TNO TPD develops a Fringe Sensor based on a 3x3 Fiber Optic (FO) coupler. A breadboard demonstrator operating around 830 nm is built. A piezo stretcher and a translation stage is used to generate the OPD. High-speed sub-nm OPD measurement is demonstrated. The influence of the visibility V of the interferometric signal is also investigated. Even for V=0.2, an OPD modulation of 0.4 nm can still be detected.
Development of a fringe sensor based on 3x3 fiber optic coupler for space interferometry
17th International Conference on Optical Fibre Sensors, 2005
Large stellar telescope is indispensable for astronomy. Aperture synthesis is a well-known technique to simulate a large space telescope by an array of small telescopes. Condition for aperture synthesis is that the light of the telescopes have to be combined coherently. Therefore, an interferometric Fringe Sensor (FS) to detect and stabilize the Optical Path Difference (OPD) between light from the different telescopes is required. TNO TPD develops a Fringe Sensor based on a 3x3 Fiber Optic (FO) coupler. A breadboard demonstrator operating around 830 nm is built. A piezo stretcher and a translation stage is used to generate the OPD. High-speed sub-nm OPD measurement is demonstrated. The influence of the visibility V of the interferometric signal is also investigated. Even for V=0.2, an OPD modulation of 0.4 nm can still be detected.
Applied Optics, 2003
Interferometry associated with an external cavity laser of long coherence length and broad wavelength tuning range shows promising features for use in measurement of absolute distance. As far as we know, the processing of the interferometric signals has until now been performed by Fourier analysis or fringe counting. Here we report on the use of an autoregressive model to determine fringe pattern frequencies. This concept was applied to an interferometric device fed by a continuously tunable external-cavity laser diode operating at a central wavelength near 1.5 microm. A standard uncertainty of 4 x 10(-5) without averaging at a distance of 4.7 m was obtained.
Fast processing of optical fringe movement in displacement sensors without using an ADC
Photonic Sensors, 2013
An interferometer based optical sensor for displacement measurement is reported. This method requires quite simple signal processing as well as least electronic components. Referring to this technique, two photodiodes spatially shifted by 90 degrees were used. The output of photodiodes was converted into rectangular signals which were extracted in LabVIEW using the data acquisition card without using an analog to digital converters (ADC). We have also processed the signals in C++ after acquiring via parallel port. A Michelson interferometer configuration was used to produce linear fringes for the detection of displacements. The displacement less than 100 nm could be measured using this technique.
Laser diode distance measuring interferometer - metrological properties
Metrology and Measurement Systems, 2012
A novel laser diode based length measuring interferometer for scientific and industrial metrology is presented. Wavelength the stabilization system applied in the interferometer is based on the optical wedge interferometer. Main components of the interferometer such as: laser diode stabilization assembly, photodetection system, measuring software, air parameters compensator and base optical assemblies are described. Metrological properties of the device such as resolution, measuring range, repeatability and accuracy are characterized.