Three-color laser-diode interferometer

Optics & Laser Technology, 2008

The coherence length of a single mode laser diode (LD) can reach more than 10 m. It allows the application of this source of light to interferometric distance measurement, with a measurement range of several meters. However, the LD's wavelength tunability, which is a result of the dependence of the lasing wavelength on the injection current, prevents the realization of the theoretically possible metrological parameters of the interferometer. In this study, we analyze the influence of a low-frequency signal disturbance, e.g., noise or disturbing modulation inherent to the injection current of the LD, on the repeatability and measurement range of an LD interferometer used for displacement measurements. Both the measurement range and the resolution of the interferometer are found to be highly limited by this factor.

Applied Optics, 1993

The author considers the resonant-mode structure of a three-wall Fabry-Perot laser-diode cavity in the context of multiple-color interferometric techniques for determining absolute distance. It is found that the theoretical emission spectrum for a dispersive gain medium such as GaAIAs in such a cavity can be used to generate synthetic wavelengths from less than 200 pAm to more than a meter with a single laser diode. The emission characteristics and their use in distance measurements are then illustrated experimentally by using a commercially available short-external-cavity device operated near threshold.

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.

Applied Optics, 1987

A method for measuring absolute distance by the wavelength shift of laser diode light has previously been proposed. In this work three serious systematic error sources for the method are discussed and some of the discussion is confirmed by experiment. The error sources are optical feedback effect, longitudinal mode distribution of laser light, and unwanted light reflected from optical devices (coherent noise). The optical feedback effect influences the wavelength shift of the emitted light. The mode distribution causes the periodic error dependent on the measured distance, and the maximum error is determined by the change in the intensity ratio of the submodes to the main mode. Coherent noise causes the periodic error also dependent on the distance, and the maximum error is determined by the amplitude ratio of the measuring lightwave to the noise. These systematic errors are observed in some demonstrative experiments.

Applied Optics, 1991

The phase ambiguity in conventional interferometers can be removed by using two laser diodes of different optical frequencies to generate a synthetic wavelength. However, the stability requirements for a two-color interferometric .laser gauge that must provide unambiguous determination of the optical fringe order over a large distance can be severe. We derive upper limits on the optical wavelength uncertainty and express them as a function of optical path difference between the object and reference beams, phase measurement errors, and the synthetic wavelength. A simple stabilization arrangement is proposed, involving simultaneous servo control of both lasers with a single Fabry-Perot etalon. The experimental implementation of the proposed system demonstrates its effectiveness for long-term (16-h) stabilized two-color interferometry over a distance of 250 mm, with a 15-mm synthetic wavelength and a repeatability of 40 nm. For periods of < 1000 s, the repeatability was 8 nm.

IEEE Transactions on Instrumentation and Measurement, 2007

We present a new method for the measurement of the absolute distance of a remote target based on the laser diode self-mixing interferometry technique, which is assisted by an electronic feedback loop that is capable of improving the measurement accuracy. The feedback loop supplies a periodic change of the emitted wavelength that exactly corresponds to a single interferometric fringe. This allows the measurement of the target distance with higher accuracy, which, in principle, is limited only by the detection shot noise and not by the fringe quantization error that is typical for the conventional fringe-counting approaches. We developed a prototype that is capable of measuring the target distance with 0.3-mm accuracy in the 0.2-to 3-m range.

Optics and Laser Technology, 2001

In this paper, the displacement of an object is measured with a photothermal phase-modulating laser diode interferometer. A feedback control system is designed to reduce the measurement errors caused by the uctuations in the optical wavelength of the laser diode and the vibrations of the optical components in the interferometer. A new method is proposed to enlarge the measuring range of displacement. Using this method, the measuring range is enlarged from half wavelength to nearly 125 m and the measurement accuracy is about 1 nm. The simulation and experimental results have shown the usefulness of the method and the feedback control system.

Chinese Optics Letters, 2017

A signal processing method of realizing a large-range displacement measurement in a sinusoidal phasemodulating laser diode interferometer is proposed. The method of obtaining the dynamic value of the effective sinusoidal phase-modulating depth is detailed, and the residual amplitude modulation is also taken into account. Numerical simulations and experiments are carried out to compare this method with the traditional one. We prove that, with this method, the sinusoidal phase-modulating laser diode interferometer can realize a centimeter-level displacement measurement range with high precision, which is much better than the traditional method.

In this paper an Absolute Distance Interferometer (ADI) for distance measurements in the range of several meters is presented. An interferometrically frequency-controlled Littrow diode laser without AR coating is employed to generate a variable synthetic wavelength. The phase-falsifying influence of electronic circuitry is discussed. First experimental results are shown.

Applied Optics, 1999

In the past few years there has been much interest in use of tunable diode lasers for absolute interferometry. Here we report on use of an external cavity diode laser operating in the visible ͑ ϳ 670 nm͒ for absolute distance measurements. Under laboratory conditions we achieve better than 1-m standard uncertainty in distance measurements over a range of 5 m, but significantly larger uncertainties will probably be more typical of shop-floor measurements where conditions are far from ideal. We analyze the primary sources of uncertainty limiting the performance of wavelength-sweeping methods for absolute interferometry, and we discuss how errors can be minimized. Many errors are greatly magnified when the wavelength sweeping technique is used; sources of error that are normally relevant only at the nanometer level when standard interferometric techniques are used may be significant here for measurements at the micrometer level.