Absolute Interferometry with a 670-nm External Cavity Diode Laser

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.

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.

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.

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.

IMTC/98 Conference Proceedings. IEEE Instrumentation and Measurement Technology Conference. Where Instrumentation is Going (Cat. No.98CH36222), 1998

The paper reports results of an investigation on the main measurement uncertainty sources in a novel distance meter based on dispersive comb-spectrum interferometry. The light source is a commercial laser diode operating at 670 nm driven under the threshold condition, and emitting a beam with a comb-shaped spectrum. Sensitivity of the measurement to the operating conditions has been evaluated. Results from an experimental activity aimed at characterizing the laser and to measure the performance of a prototype implementation are also presented. The system is suitable to perform unambiguous non-incremental distance measurements over a range of 0.8 mm with a total uncertainty of about 1.5 pm.

In this paper, we suggest a novel system that is capable of measuring absolute distances with an uncertainty of one micrometer, or better, over a distance of up to 20 meters. This system consists of a Michelson interferometer, a tunable external cavity diode laser, a wavelength meter, a digital camera and a computer. The Michelson interferometer contains a reference arm mirror, a target arm mirror, a coherent light source, a white screen and a beam-splitter. The distance between the beam-splitter and the reference arm is known a priori with one-micrometer accuracy. The distance between the beam-splitter and the required measurement target arm is initially known with only a low precision accuracy of one-millimeter. The distance between the beam-splitter and the target arm is required to be measured with one micrometer uncertainty, or better. Index Terms— Absolute distance measurement, external cavity tunable diode laser, Fourier fringe analysis, Michelson interferometer, synthetic wa...

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.

2009

AMIT RAVINDRA SURATKAR. Absolute Distance (Thickness) metrology using wavelength scanning interferometry. (Under the direction of DR. ANGELA D. DAVIES) Wavelength scanning interferometry offers a new dimension in precision metrology by measuring the cavity length (thickness), the cavity length variation over the cavity area (flatness), and the optical homogeneity within a transparent cavity; without any mechanical movement by implementing a tunable laser. This property is useful when the physical movement of an optic is not feasible using traditional phase shifting methods employing piezoelectric transducers and for characterizing solid optical cavities which require movement of one surface relative to the other. The cavity length that can be measured is limited by the wavelength scanning range a smaller cavity requires a larger tuning range. Tunable lasers are now available with very large tuning ranges in the near infrared, potentially extending the measurement range significantly...

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.

Proceedings of SPIE - The International Society for Optical Engineering, 2008

Coherent absolute distance interferometry is one of the most interesting techniques for length metrology. In frequency sweeping interferometry (FSI), measurements are made without ambiguity, by using a synthetic wavelengths resulting from a frequency sweep. FSI-based sensors are simple devices and fulfill an important role on any demanding space mission metrological chain. Their parameterization flexibility allows either technological or application-related tradeoffs to be performed.